"LI B RARY OF THE UNIVERSITY OF ILLINOIS 666 ^. 16-23 CENTRAL CIRCULATION AND BOOKSTACKS The person borrowing this material is re- sponsible for its renewal or return before the Latest Date stamped below. You may be charged a minimum fee of $75.00 for each non-returned or lost item. Theft, mutilation, or defacement of library materials can bo causes for student disciplinary action. All materials owned by the University of Illinois Library are the property of the State of Illinois and are protected by Article 16B of Illinois Criminal Law and Procedure. TO RENEW, CALL (217) 333-8400. University of Illinois Library at Urbana-Champaign MAY 2 9 2001 When renewing by phone, write new due date below previous due date. L162 UNIVLR5ITY OF ILLINOIS BULLLTIN Vol. X. SEPTEMBER 9, 1912. No. 2 [Lntered February 14, 1902, at Urbana, Illinois, as second-class matter under Act of Congress of July 16, 1894.] BULLLTIN No. 16 DLPARTMLNT OF CERAMICS A. V. BLE.ININGLR, Director COBALT COLOR5 OTHLR THAN BLUL BY R. T. STULL AND G. H. BALDWIN INFLULNCL5 OF VARIABLE 5ILICA AND ALUMINA ON PORCELAIN GLAZE5 OF CONSTANT RO BY R. T. STULL INVESTIGATIONS ON THE DIELECTRIC STRENGTH OF SOME PORCELAINS BY B. S. RADCLIFFL 1911-1912 PUBLISHED FORTNIGHT .Y BY THE UNIVERSITY >A 7io.lL-23 [Reprinted from Transactions American Ceramic Society, Vol. XIV, by Permission.] COBALT COLORS OTHER THAN BLUE. By R. T. Stull and G. H. Baldwin, Ceramic Laboratories, University of Illinois. INTRODUCTION. The color imparted to a glass or glaze depends upon the kind of coloring oxide, the composition of the batch and the manner of heat treatment. It has been considered that cobalt is per- sistent in producing blue under all conditions. Since two or more distinct colors are obtainable from all other coloring oxides under different conditions, there seemed to be no logical reason why some color other than blue could not be obtained from cobalt oxide. Since cobalt oxide has so persistently given blue colors under normal ceramic practice, it was evident that a departure in com- position must be made from the ordinary commercial types of glazes if a color different from blue was to be developed from cobalt oxide. A speculation as to the possible colors obtainable from cobalt oxide as the sole colorant is of interest. Cobalt salts in solution under certain conditions impart pink, while under other conditions the color imparted is blue. It, therefore, seemed possible to de- velop all the different shades from blue on one hand to pink or even light red on the other. The problem was to develop a type of glaze that would bring out the pink or red color if such were possible, and the key to the situation was found in blowpipe analysis. Magnesia and magnesium minerals containing cobalt, when powdered, moistened with a solution of cobalt nitrate and heated, give a pink color. Alumina and alumina minerals containing cobalt, when similarly treated, give blue. This suggested a glaze high in magnesia and free from alumina. It was recognized that if such colors could be produced they would be of greatest value for low temperature work. Since a high content of magnesia imparts refractoriness to a glaze, it would be necessary to introduce a "softener" which would not in- fluence the color toward the blue. Of the two "softeners," PbO and B,0 3 , tried in a preliminary test, 1 it was found that the 1 Vol. XII. Trans. A. C S., pp. 707-708. COBALT COLORS OTHER THAN BLUE. former changed the magnesia-cobalt pink to blue, while the latter did not, hence B 2 3 was selected as the "fluxing" or "softening" agent. EXPERIMENTAL WORK. First Group. — The first group of glazes was made in order to develop workable members over a range of temperatures. In this group the RO remained constant, the Si0 2 and B 2 3 being variables. The limits covered were o . 2 Na 2 o . 6 MgO o . 2 CoO o to i.o B 2 0„ i .o to 4.0 Si0 2 . Twenty-four glazes were made in this group. The horizontal series are designated by letters and the vertical series by numbers (see charts). The formula and batch weights of the four corner glazes are: Formulae Batch weights q O c O c O u M c "5 C 4-» z § pa CO Z £ u m h A-i 0.2 O.6 0.2 1 .0 2 12 504 165 600 A-6 0.2 O.6 0.2 1 .0 1 .0 212 504 165 1240 600 D-i O. 2 O.6 O. 2 4.0 212 504 165 2400 D-6 O. 2 O.6 O. 2 1 .0 4.0 212 504 165 1240 2400 The four batches were weighed, ground dry for one hour, fritted and ground to pass 120 mesh. The different members in the group were made by blending the four extremes according to their combining weights. Since the glazes settled rapidly and caked, it was found necessary to employ a "colloid" in order to induce flotation for application and adhesion on drying. Glucose, dextrine and glue were tested. The best results were obtained with 4-5 per cent, glue. Such large quantities of either glucose or dextrine were required in order to produce free flotation that the glazes cracked and curled up on drying. With glue, however, a high degree of flotation was obtained, and the glazes dried without cracking. The glazes were applied in a thick coat on 2" porcelain discs previously burned to cone 1 1 . Three burns of this group were made, viz., cones 2, 4 and 7 (Charts 1, 2 and 3). At cone 2 COBALT COLORS OTHER THAN BLUE. T/^A/s. s4/w. C£~s? sac ro/L . ^/^ srt/£ s. <*• 0^/.a^/M mm A/ A2 A3 A<4- <4^ y^e Q \ \ <& % ^ Q S S Q Q X A7/ £?^ /P^ Z?<4- £?^ £><5 ^1 C/ Cf. C^/?. >SC?C. y

Jl tV/A/ . GAst&O \ CO/VST^ A/7~ ^^^ 2C OOJ /-5» 1/ re 13 i^- i^ ■/ SZ jE3 ^<4- <0 S S x ^ ^ 12 COBALT COLORS OTHER THAX BLUE. Formulae Batch weights O § o so 5= <-> pq o 35 a M S s to q E-i 0.2 o.6 0.2 o.6 o-5 212 504 165 744 300 E-5 O. 2 o.6 O. 2 i-4 °-5 2 12 504 165 i860 300 I-i O. 2 o.6 O. 2 o.6 i-5 212 504 165 744 900 1-5 0.2 o.6 O. 2 1.4 i-5 212 504 165 i860 900 Three burns were made, viz., cones 02, 1 and 3 (Charts 4, 5 and 6). The red-violet color was well developed in all cases except in vertical series 1, containing 0.6 B 2 3 , which remained persistently matte in all three burns. Crystalline patches appear in all pieces where well matured. The red- violet color is more prominent where crystallization has taken place. Decreasing Si0 2 and increasing B 2 3 tends to throw the color toward the red and away from the blue the same as observed in the first group. Where the glazes are overtired, they have "run" con- siderably, attacked the body and give a clear blue. Occasionally a small group of red- violet crystals appear in a clear blue field. Several of the glazes in this group were applied to porcelain bisque vases. In all cases where the glazes did not flow ex- cessively or where crystallization appeared, the red-violet color was prominent. Where excessive flow took place the glaze remaining on the surface of the vase was a clear blue. In several cases where the glaze flowed down over fire clay "buttons" used as setters, the color of the glaze on these buttons was a dark green. The best glazes in the group are H3.E4, E5, F 3, F4, F5, G 3 , G 4 and G 5 . Member F 4 appeared to be the best one in all three burns. Third Group. — A third group was made in order to obtain lighter shades of the red-violet color. Since F 4 seemed to hold the color so persistently and showed a fair range of temperature, it was selected as the starting point. Lighter shades can be produced by blending F 4 with a similar glaze but containing no cobalt oxide. The first problem to solve was to produce such a glaze having the same heat range and fusibility as F 4. In order to save time it was decided to make a triaxial group (Chart Purple Produced by Use of Cobalt 0.2 Na 2 O 1 G-5 at cone 2 0.6 Mg O \ 1 .4 B 2 3 1 Si 2 0.2 Co O COBALT COLORS OTHER THAN HLUE. 13 ^^^^^\^r>rmi 7) by placing F 4 at the upper apex, and the two following color- less glazes at the lower corners: 0.2 Na,0 ) _ ^ „._. 0.5 Na„0 ) _. n _._ „ „ ' > 1.5 B„0, 0.75 SiO, ° . T " \ o.q B,0, 0.75 SiO, o . 8 MgO ) ° 2 ■' /0 " 0.5 MgO ) v 2 J ' ° The only constant member in the group is Si0 2 at 0.75 molecule. The group was made by fritting the three extremes and blending as was done in the two preceding groups. Glazes were applied to porcelain discs and burned to cone 02. Examination of the trials indicates that there is no difference in shade or intensity of color from a content of 0.1 CoO to 0.2 CoO. The glaze near the lower left corner is a dark lavender while the one near the lower right corner is clear blue. As the MgO and B,0 3 decrease and Na,0 increases, the color tends toward blue. Wherever crystallization appears, the red- violet or a lighter shade tending toward lavender appears. 14 COBALT COLORS OTHER THAN BLUE. CONCLUSIONS. The color violet is composed of equal intensities of red and blue. Most of the colors produced in the foregoing work lie be- tween the violet and the red. A fusion of either soda or boric oxide and cobalt oxide gives blue. Cobalt silicate is blue. A mixture of magnesia and cobalt oxide heated to redness gives pink. The color darkens tending toward red as the temperature of calcination is increased; the color change, however, is not pro- nounced until very high temperatures are reached. The red-violet, lavender or pink color is apparently due to some combination of magnesia with an oxide of cobalt. De- creasing MgO or increasing Si0 2 causes diminishing red and in- creasing blue. This would indicate that the silica has broken up the magnesia-cobalt combination, thus imparting the cobalt- silica blue. Although a fusion of B 2 3 and CoO gives blue, an increase in B 2 3 in the foregoing glazes tends toward the red and away from the blue, indicating that the magnesia-cobalt red-violet color is not only stable in the presence of B 2 3 but that the latter en- courages the red by some action not definitely understood. DISCUSSION. Mr. Wilder: I would like to ask what would be the result of increasing the heat in the trials shown on the last diagram? Mr. St nil: You would tend to get less of the red-violet or lavender and more of the blue. This is probably due to the fact that the glaze becomes very fluid as the temperature increases and attacks the body vigorously. The alumina taken up changes the color to blue. We intend to continue further and try what we call an insulating glaze, by biscuiting the porcelain at 05 to 02, then applying a glaze similar to the first one on the board, as, for example : U a a 1 *SiO.. rMgO ) In this glaze x, y and z must necessarily be determined experi- mentally in order to fit working conditions. After applying the insulating glaze to the soft biscuit, the body is to be vitrified at cone u or cone 12, then the colored glaze is to be applied and COBALT COLORS OTHER THAN BLUE. 1 5 burned to maturity. In this way we hope to exclude alumina from the glaze. Mr. Wilder: I would like to ask Professor Stull if he ever tried to make pigments by calcining the magnesia? Mr. Stull: No, I have never done that. Mr. Landrum: I made pigments by calcining iron oxide with magnesia; but I never decided whether there was a com- pound formed or not, nor whether there was a red-violet color from the magnesia and the ignition simply gave a more homo- geneous pigment. I think there should be some trials made by igniting at a little higher temperature. Mr. Stull: If the color so obtained were stable, it would work all right, but apparently these colors are very unstable during fusion in the presence of silica and alumina. It seems to me that it would be possible to make over-glaze colors along this line, if they are not fired too high and thus made too fluid. The white sample in the right-hand lower corner of the triaxial is very fusible and has attacked the body vigorously as it is pitted in places. Therefore, the over-glaze colors would have to be fired with caution, or so constituted as to possess a wide heat range. Mr. Will: I make blue stains of various composition which in cone S and cone 10 fire turn out a pink-violet, a beautiful color, but the invariable experience has been that on being used as colors under a full glaze they turn to a deep blue. In other words, the red color is not stable except with a matte glaze. For instance, use same as a stain for a matte glaze, or a semi- matte underfired, and you get a pink glaze. From this, purple glaze is often produced by overfiring, and on firing to a gloss the same piece will show a blue color. Mr. Bruner: I would like to ask a question in regard to Chart 7. Professor Stull, do you wish to give us the impression that in the lower left-hand corner, the effect was due to low soda, high magnesia, high boric acid, and that if handled cor- rectly, these glazes will give the pink color and on the other hand with low magnesia and low boric acid, the blue color comes out? Mr. Stull: That is right. Mr. Bruner: Are all those pieces exposed to just about the 1 6 COBALT COLORS OTHER THAN BLUE. same heat or would you say their color was due to their position in the kiln? You do not mention anything about the fusibility and the possibility of the glazes being much more fused in one end of the kiln and the fact that when you have that condition it naturally leaves the color blue. On this piece (indicating number) you have a beautiful red-violet, as you call it, but in- side it is blue. Even around the edges here you can see a little of the blue. Mr. Stull: Underneath the red-violet glaze there is a thin film of blue next to the body, and where the glaze is thin the blue shows through. When crystallization takes place it brings out the red-violet color, and underfiring also brings out the char- acteristic red-violet color. On the inside of the piece, the thin glaze has attacked the body, thus giving the characteristic cobalt- alumina blue. Mr. Will: I have applied one of these reddish blue colors to glazed Belleek ware and fired it again at glost kiln heat (cone 4-5) and there also one could not help noticing the phenomena of crystallization and the bringing out of red spots where under- fired, while the balance of the piece showed a strong deep blue glaze with a high gloss. Mr. Burt: I notice a number of these samples seem to show a distinct crystallization wherever the pink occurs, and I wondered whether Mr. Stull had examined it with that in mind. You get blue on the inside, but on the outer surface where you have sufficient surface glaze, you produce crystallization phenomena which develop this pink crystal. Is not the color something of a crystallization phenomenon ? Mr. Stull: It is true that the crystals do show the color, but the red-violet color is also developed in an underfired glaze and blue in an overfired glaze, or where the glaze is thin and has "fluxed into the body." On Chart 1, in the upper left-hand corner is the most refractory glaze in the group. It is as soft as chalk, yet it shows a light red- violet color. Alumina and cobalt together at a red heat will give a blue, while magnesia and cobalt will give pink. I do not know whether it is a chemical or a physical action that brings out the blue in one case and the pink in the other. [Reprinted from Transactions American Ceramic Society, Vol. XIV, by Permission.] INFLUENCES OF VARIABLE SILICA AND ALUMINA ON PORCELAIN GLAZES OF CONSTANT RO. By R. T. Stull, Ceramic Laboratories, University of Illinois. INTRODUCTION. Porcelain glazes of the Seger cone formula type are the most inexpensive to produce synthetically, have a comparatively wide range of maturing temperature and give but few defects. These are offered as the principal reasons for the comparative meagerness of literature pertaining to investigations on glazes of this type. Seger 1 gives the following as glaze formula commonly used for porcelain: RO, ( i to 1.25) ALA,, (10 to 12) Si0 2 and for Seger porcelain 2 RO, 0.5 A1,0 3 , (4 to 6) Si0 2 Prof. Orton 3 gives the following limits for characteristic porcelain glazes : 0.1 too.5 K,0) . , _ _._ n n> C°-5 to I2 5 ALA, 4-0 to 12.5 SiO, 0.9 to 0.5 CaO j z * 02 EXPERIMENTAL WORK. In a study of porcelain glazes 4 of the cone formula type, two groups were made in order to illustrate the influences of variable silica and alumina. The first group covered the limits _ - V0.3 to 1.0 A1,0 3 [ i-S to 7.2 SiO, and comprised eight horizontal series, from A to H, containing eighty glazes in all. The glazes in that portion of the field covered by the A to H series were made by blending the four extremes according to their combining weights. The formulae and batch weights of these extremes are: 1 Vol. II. Translations Seger, p. 705. 2 Ibid., p. 706. 3 Glaze lectures at Ohio State University, 1901-2 4 W'jrk done by classes 1911 and 1912, University of Illinois. 1 8 INFLUENCES OF SILICA AND ALUMINA ON PORCELAIN GLAZES. O O d O d 3 d in 2 a « d Clay 5 Glaze ■ 6 do = O A-I A— 10 0.3 o-3 0.3 o-3 O.7 O.7 O.7 O.7 0.3 0.3 1 .0 1 .0 1.8 7-2 1.8 7.2 167 . 1 167 . 1 167 . 1 167 . 1 70.0 70.0 70.0 70.0 yo.3 90.3 109.2 324 240.0 H-i H-io Glazes in the W to Z series were also made in the same manner with the exception that it was necessary to employ a frit in order to introduce the excess K 2 which could not be furnished by feldspar. The formulae and batch weights of the four ex- tremes are: u 3 a £ O O O w ■0 O c W < w to to {. -t7K /fADCLlEFE ^2 s ' s ^ / / /. ,s i' / ' ,< sV VOLTAGE- TH/C/f/VESS CC&KE &Uf?/V/HO TEMP come /a£ /? >' s ,' e ' TE/V/V. B-4LL. CS-y* K A/o. / >o V <. ,' ' EA/OL/S/-/ C/-l/A/-^ C£.s*r ss FL/A/T OH/O S fi/f 20 A \ /DC w -,,-* TOOO M OOO ■*. xx>o so 000 SOc 1 70t 700 80 OOO 90 ?oc 1 /aooc V ^0/-7>^OE Calculating the average puncture voltage per mm. thick- ness for all trials tested, assuming that the puncture voltage is directly proportional to the thickness, gives a voltage of 14,525. This point is plotted and the heavy dotted straight line passes DIELECTRIC STRENGTH OF PORCELAINS. 2 9 from the origin through it. Owing to the fact that a voltage higher than 100,000 was not available, pieces over 6 l / 2 mm. in thickness could not be tested. However, the limits covered exceeded the requirements in the future tests. Some interesting results were obtained by puncturing the same test piece repeatedly in the same spot. One piece, 5.7 mm. in thickness required 83,800 volts, and was given a second test and punctured at 79,000 volts, a third test required 59,300, a fourth 51,200. When the trial was shifted to a new place, the voltage required to puncture it was 77,500. Other trials were treated in the same manner giving similar results. Repeated tests through the same line of puncture weakened the dielectric strength at that point, but not until several punctures did the porcelain become too weak to resist a fairly high voltage. Apparently the current fuses the porcelain in passing. Upon breaking several pieces through the line of puncture a glassy appearance was always noticeable. INFLUENCE OF VARIABLE HEAT TREATMENT. There seems to be no data available pertaining to the effect of rate of burning and cooling upon the dielectric strength of porcelains. In order to throw some light upon this subject, four porcelain bodies were selected from the work of Bleininger and Stull on "The Yitrifi cation Range and Dielectric Strength of Some Porcelains." These bodies are here designated by A, B, C and D. Besides these, E was made by blending the four. Body Georgia Term. X. Car kaolin ball Xo. 1 kaolin Eng. China Potash Ohio clay No. 7 feldspar flint A 50 B | C | D | E | 5 55 55 27 40 10 15 30 25 20 60 20 20 IS 23 18 Five more bodies were made similar to these except that soda feldspar replaced the potash feldspar by theoretical mole- cules. These bodies are designated as Ai, Bi, Ci, Di, and Ei. Twenty trials were made from each of the ten bodies. These 3Q DIELECTRIC STRENGTH OF PORCELAINS. trials were divided into four sets, each set containing five trials made from each body. Each set was burned and cooled under different conditions. Set i was burned to cone 10 in six hours and cooled slowly in order to determine the effect of quick firing and slow cooling. Set 2 was burned to cone 13 in six hours after which air was passed through the kiln cooling the temperature down to cone 02 in one hour. The kiln was then allowed to cool slowly. Set 3 was burned to cone 10 in six hours then the temperature was gradually raised to cone 12 in an additional 14 hours, then carried rapidly to cone 17 and held for 2 hours. The kiln was then allowed to cool slowly. Set 4 was burned to cone 10 in 6 hours, gradually raised to cone 13 in an additional 18 hours and held for 20 hours. The kiln was then cooled down to cone 2 in five hours, then allowed to cool slowly. C and Ci in the first burn showed 2 per cent, porosity but all the other bodies were well vitrified. AVERAGE VOLTAGE PER MM. REQUIRED TO PUNCTURE TRIALS. Body Part 1, Cone 10 Part 2, Cone 13 Part 3, Cone 17 Part 4. Cone 13 A Ai B Bi C Ci D D, E Ei 13260 12840 134OO 14000 IO32O 9180 14540 13400 !355Q 13560 13 1 20 13100 13COO 13640 13960 13220 1 3 150 13920 13470 14820 12600 14300 13500 13620 12760 13820 13680 I 3 ICO 1466 ) 14100 13070 13870 13000 14160 1 3 1 80 13860 14100 135^0 12850 13860 The tests show that there is not a very wide difference in the dielectric strengths of the different bodies or in the manner of heat treatment. By taking the average puncture voltage per mm. for each different body for the four different burns (excluding C and Ci which were porous in the first burn), we have the following table which shows that the soda feldspar bodies have higher dielectric strengths than the corresponding potash feldspar bodies in all cases except in bodies D and Di in which case D shows a higher dielectric strength than Di. DIELECTRIC STRENGTH OF PORCIvLAIXS. 31 Potash Average Average Soda spar voltage voltage spar bodies per mm. per mm. bodies A '.!"!- '33 27 A-i B 13225 13855 B-i c 13300 13633 C-i D 13867 13485 D-i E 13632 14185 E 1 In order to get a comparison of the effects of variation in heat treatment, the average voltage per mm. is taken of the ten bodies for each of the four different burns. In averaging the first burn, bodies C and Ci are rejected on account of their porosities. The percentage variation between maximum and minimum puncutre voltages is less than 0.55 per cent, showing that the dielectric strength was substantially unaffected by the variations in burning and cooling from cone 10 to cone 17. Burn Cone Average puncture voltage per mm. Part I Part II Part III IO 13 17 13 13569 13540 I 3614 Part IV i S547 FIRE CLAYS AS RAW MATERIALS FOR HIGH TENSION INSULATORS. The trade demands a white porcelain body for high tension insulators. Frequently a dark colored glaze (usually brown) is called for. If a colored body could be employed containing a high per cent, of fire clay, a cheaper body and a more uniform color of glaze would be the result. Insulators made from No. 2 fire clay or stoneware clay do not show a high dielectric strength. These clays vitrify at or near cone 8 while the white high tension porcelain insulators vitrify around cone 12. In order to obtain bodies which would vitrify near cone 12, three fire clays were blended triaxially (Fig. 4). The three fire clays selected were: Olive Hill flint fire clay (calcined); Olive Hill Xo. 1 plastic fire clay; Bloomingdale 2 No. 2 plastic fire clay. 2 An excellent stoneware clay, vitrifying at cone 8. 32 DIELECTRIC STRENGTH OF PORCELAINS. rt?ANS AM C£f? SOC VOL X/\s F/& ■>£ RADCUFFE JOO-FL/A/rCt-Ar '/OO - /VS / PCASr/C /OO -A/S 2 &LAST/C Five trials of each body were made and burned to cone i2 1 / 2 .. The porosities and puncture voltages were determined and aver- aged. These results are plotted on the triaxial diagram (Fig. 5), the dotted lines representing porosities and the heavy solid lines puncture voltages per millimeter thickness. The results show that 90 parts No. 1 plastic fire clay and 10 parts calcined flint fire clay give a body of the highest dielec- tric strength at cone i2 1 / 2 , and even though this body had 1 per cent, porosity, it compares very favorably with the best white porcelains in strength, 14,000 volts per mm. being required to puncture it. When No. 2 fire clay or stoneware clay replaces the No. 1 plastic clay, the flint clay remaining constant, the dielectric strength is lowered even though the porosity is lowered at the same time. Bodies containing 50 per cent, or more of No. 2 clay showed evidences of a "bleb" structure, which weakened them, causing them to puncture at a low voltage. The substitution of 10 per cent. No. 2 clay for No. 1 in body 31, which gives body No. 32., DIELECTRIC STRENGTH < >F PORCELAIN'S. 7~/Z4jVS AWOW SOC. M/. X/IS /PPLAT/l/E PO/?05/7/£S AV/P r/&E:C£AY'ML>(rC//i'£S &V/W££> TO C0/V£ /£, ££ //V7- £//?£ ClAy 33 Ato.2 />Ls4ST/C r//?£C^Ay did not materially lower the porosity, yet it lowered the puncture voltage from 14,000 to 12,500. Trials which were subsequently made from bodies 14, 22 and 31 and burned to cone 14 gave a porosity for 14 of 1.34 and a puncture voltage of 13,600 per mm. The porosity of No. 22 was 0.08 and its puncture voltage 14,100 per mm. Porosity of No. 31 was zero and its puncture voltage 14,600, an increase in voltage of 600 for a decrease in porosity of 1 per cent. The white porcelain body of highest dielectric strength found in the foregoing work is the soda feldspar body Ei, giving a puncture voltage of 14,820 per mm. in the part II burn. The potash feld- spar body of highest dielectric strength is D, showing a puncture voltage of 14,660 in the part III burn. In so far as dielectric strength is concerned, the foregoing 34 DIELECTRIC STRENGTH OF PORCELAINS. evidence indicates that vitrified bodies made from refractory fire clays stand on an equal footing with white porcelains for high tension insulators. Good colored high tension insulators can be made from a body composed of No. i plastic fire clay (part of which may be calcined) and a small amount of feldspar to assist vitrification. The use of flint fire clay in the body lowers the dielectric strength by increasing porosity through its refractoriness. The plasticity, working properties and shrinkage of a fire clay body can be con- trolled much better than white bodies and at the same time, it would be cheaper in composition. INFLUENCE OF LIME ON DIELECTRIC STRENGTH. In order to determine the effect of lime upon the dielectric strength of porcelain, the following bodies were made in which CaC0 3 was used to vitrify the bodies in place of feldspar. Part of the clay was calcined in order to control working properties. The trials were burned to cone 14 and porosities and puncture voltages determined. These results are given in the following table. Body Tenn. ball C No. 1 N. Car. kaolin Ohio flint Calcined N. Car. kaolin CaCQ 3 F. . Fl. F2. F 3 . F 4 - F 5 - F6. F?. F8. 10 10 10 10 45 45 45 45 45 45 45 45 45 23 20 19 18 17 16 15 The results show that 6 per cent. CaC0 3 has produced a non- porous body at this temperature which does not show a high dielectric strength, and that each increase in CaO has increased the dielectric strength. F5 containing 5 per cent. CaC0 3 has a porosity of 12.84 per cent. F6 shows that an increase of 1 per cent, of CaC0 3 has lowered the porosity to almost zero. DIELECTRIC STRENGTH OF PORCELAINS. 35 Body Per cent, porosity Average voltage per mm. Body Per cent porosity- Average voltage per mm. F. Fi. Fa. F 3 28.02 27.60 20.52 F4- F 5 - F6. F7. F8. 12.65 12.84 0.05 0.03 0.06 5000 6000 6700 8000 When the puncture tests of F6, F7 and F8 are compared to those of feldspar porcelains of the same porosities and burned at the same temperature or even a little lower, it is observed that the dielectric strengths of the feldspar porcelains are from one and one-half to twice those of the lime porcelains. CONCLUSIONS. Conclusions which may be drawn from the foregoing work indicate that: 1. For all practical purposes, the dielectric strength is proportional to the thickness of the porcelain, which is in con- firmation of that assumption. 2. Rapid burning or slow burning, rapid cooling or slow cooling do not materially affect the dielectric strength of high tension insulators so long as such treatment does not develop blebs, cracks or other flaws. 3. The average of all tests made in this work showed that the molecular substitution of soda feldspar for potash feldspar in a porcelain decidedly increased the dielectric strength. 4. High-grade fire clays are capable of making high tension insulators giving as high a dielectric strength as the average potash feldspar porcelain vitrifying at the same temperature. 5. The substitution of a stoneware clay for No. 1 plastic fire clay lowers both the maturing temperature and the dielectric strength. 6. A body made vitreous by the use of lime without feldspar gives a porcelain of low dielectric strength. DISCUSSION. Mr. Purdy: I note that he has a series in which calcium carbonate is varied against calcined clay. An explanation of the 36 DIELECTRIC STRENGTH OF PORCELAINS. philosophy of a substitution of such unlike materials would be of interest. I note also that he reports that a piece which has already been punctured will show a lower but relatively high strength when tested the second time at the same point and the same high strength when the same test piece is punctured at a new point. The only fact of value in these observations is the efficiency of oil as a non-conductor. When puncturing under oil the hole thus caused is filled with oil and not by glass as Mr. Radcliffe thinks. You can not re-test a punctured piece in the air as they did in the oil. In fact they could not have tested those shallow pieces in the air at all because of arcing around. Their data, therefore, on these two points is of value only for insulation under oil. Their conclusion should have been that their porcelain test pieces had but little, if any, better dielectric strength than did the oil they were using. Prof. Siull: In order to satisfy Prof. Purdy's interest re- garding the replacement of calcined clay by calcium carbonate, I will say that the calcined clay was employed merely for con- trolling the working properties and drying shrinkages of the bodies, as was mentioned when the paper was read. No attempt whatever was made to get a comparison of the bodies by variable lime-calcined clay. The object in view was merely to obtain vitreous bodies by using lime without resorting to additions of feldspar, and to compare the dielectric strengths of these lime bodies with those of feldspar bodies previously made. There is no "hole" left after the porcelain has been punctured. Several of these crock shaped test pieces, after puncturing, were used as convenient receptacles for calcining small samples of kaolin at iooo° C. At this temperature the oil was com- pletely burned off. Some of these trial pieces were broken through the line of puncture after they had served their purpose in calcining clay and these pieces showed plainly that the "hole" was filled with a glass. Mr. Radcliffe shows that repeated puncturing through the same spot gradually weakens the dielectric strength. If punctur- ing leaves a hole and this hole is filled with oil, then why would DIELECTRIC STRENGTH OF PORCELAIN'S. 37 not repeated puncturing after the first give the same voltage readings for puncturing the column of oil filling the hole? The use of the oil bath is merely to prevent arcing. If the trial pieces had been made of suitable size and shape to prevent arcing when tested in air, there is no reason why they would not have shown the same dielectric strengths in air as they did in oil. The results are comparative whether the porcelains are tested in air or in oil. Either set of conditions would show the porcelains of highest dielectric strength. NOTES PREPARED AFTER READING THE PAPER. Mr. Minncman: This paper by Mr. Radcliffe is a valuable addition to our ceramic literature, for the reason that so little experimental data is available along these lines. I think, however, that certain of his conclusions are drawn too directly from his actual results, neglecting other conditions which are bound to enter in. In regard to the dielectric strength of soda-feldspar versus potash feldspar, Mr. Radcliffe says: "The soda feldspar bodies have higher dielectric strengths than the corresponding potash feldspar bodies" and "The average of all tests made in this work showed that the molecular substitution of soda feldspar for potash feldspar in a porcelain decidedly increases the dielectric strength." However, upon looking over the individual test results, it is seen that in eleven cases the corresponding soda feldspar bodies show higher dielectric strength while in the remaining eight cases the corresponding potash feldspar bodies show the higher dielec- tric strength. Averaging the dielectric strengths of all the soda feldspar bodies and all the potash feldspar bodies, we find the soda feldspar bodies have only about 2.5 per cent, higher dielec- tric strength than the corresponding potash feldspar bodies. This appears to be a decided increase in the dielectric strength, but when it is remembered that, in the method used in testing, voltage readings accurate to several per cent, are almost impossi- ble, and variations up to 10 per cent, are quite possible, this difference of 2.5 per cent, seems almost negligible. The voltage readings in these tests were taken, I under- stand, from a voltmeter placed across the low tension side of the 38 DIELECTRIC STRENGTH OF PORCELAINS. transformer, getting a calibration curve between the volts pri- mary and volts secondary by means of a needle gap in the high tension side. The readings could, therefore, not be more accurate than readings from the needle gap which would be from one to four per cent., depending upon the experience of the observer. Add to this numerous uncontrollable variables, such as varying weather conditions, growth of charge in the circuit, variation in wave form and the time element in testing and it is evident that a wide divergence is quite possible. That such a variation occurs, may be seen from the results obtained by Messrs. Bleininger and Stull, Vol. XII, Trans. A. C. S., p. 638, who made tests on the same porcelains fired at approximately the same heat treatment and tested with the same, or a very similar, apparatus. Comparing their results on the same trials and with Radcliffe's results we find variations up to 25 per cent. Considering these points, I should say that Mr. Radcliffe's results tend to show that the dielectric strength of a porcelain is the same whether made from soda feldspar or potash feldspar so long as the porcelain is well vitrified and dense. In regard to the use of lime, Mr. Radcliffe concludes that "a porcelain made vitreous by the use of lime without feldspar gives a porcelain of low dielectric strength." It must be remembered that Mr. Radcliffe replaced his feldspar with lime and calcined china clay, thereby making a body of an entirely different structure. It is evident that a body made up with calcined clay and lime in place of feldspar would behave quite differently, due to the lesser distribution of the lime particles and the resulting differences in fusion, just as a body made up with equivalent amounts of sodium carbonate and calcined clay would differ from a body made up with soda feld- spar. Had the clay and lime been fritted and ground until a homogeneous mixture was reached before being used in the porce- lain, I think that entirely different results* might have been ob- tained. I agree with Bleininger and Stull that dielectric strength "depends more upon sound vitrification and good mechanical structure than upon chemical composition." DIELECTRIC STRENGTH OF PORCELAINS. 39 Mr. Radeliffe's results do, however, show that lime used in porcelain in this way materially shortens the firing range. The great volume of high voltage porcelain is not used under oil but in air and tests under oil often give entirely different results than do air tests. It is particularly noticeable that a porcelain not completely vitrified and having considerable ab- sorption shows up very well when tested under oil, but breaks down much earlier when tested in air with the bottom of the test piece placed in water as is done in commercial tests. .Mr. Radcliffe mentions the puncturing of a piece under oil repeatedly in the same spot. When testing porcelain in air, after puncture once takes place there is a continuous flow of the current, and the piece ceases to act as an insulator. When testing under oil, however, this repeated puncture at a lower voltage often takes place, which leads me to believe that the oil protects the punctured spot sufficiently to give considerable insulation after the first puncture. Consequently I should say that tests made in air, more nearly approximating conditions under which high voltage porcelain is used commercially, would be of much more practical value. Prof. St nil: The question of experimental errors enters into all research work of this character. In theory, however, there is such a thing as absolute accuracy. The value of research work depends largely upon the accuracy in executing the work and the extent to which experimental errors are avoided or elimi- nated. One of the greatest sources of error which Mr. Minneman failed to mention is due to variations in structure of different pieces made from the same body. It is impossible to eliminate minute air bubbles and to mould two pieces of porcelain so that they will have identically the same structure. Where it is impossible to eliminate experimental errors or to deduct such errors by calculations from known data, it is customary to make several tests and to consider the mean average as a means of reducing such errors to a minimum. As has been mentioned, Mr. Radcliffe made from five to ten different puncture tests for each different body under each differ- ent set of conditions, excluding all trials in which Haws due to 4-0 DIELECTRIC STRENGTH OF PORCELAINS. moulding were apparent and taking the mean average of ap- parently sound pieces. Mr. Minneman states that "it is seen that in eleven cases the corresponding soda feldspar bodies show higher dielectric strength while in the remaining eight cases the corresponding potash feldspar bodies show higher dielectric strength." It was stated in Mr. Radcliffe's paper when read that "bodies C and Ci are rejected on account of their porosities" (in the first burn). Since these two bodies are porous they are not at all comparable with the others which were well vitrified, hence, it is legitimate and proper to exclude them from the calculations. Excluding C and Ci in the first burn, it is observed that the com- parison is as twelve to seven, as Mr. Minneman has evidently made an error in count. Since five trials of each porcelain for each of the four burns were tested, the average puncture voltage per mm. (excluding C and Ci in the first burn) is calculated on ninety-five trials punctured for each type of porcelain. Taking the average of such a large number of tests tends to give an accurate com- parison. The physical properties of ceramic mixtures depend upon composition and method of treatment. The treatment of the potash feldspar porcelains and the corresponding soda feldspar ones were carried out as nearly alike as possible. Since the two different kinds of feldspars are bound to exert some differences upon the physical properties, and one of these physical properties is "dielectric strength," it is more logical to conclude that the substitution of soda feldspar for potash feldspar has increased the dielectric strength since this conclusion is backed by the average results of ninety-five puncture tests of each of the two types of porcelain. Mr. T. H. Armine: The puncture tests made upon the porcelains referred to in Mr. Radcliffe's paper were made under my supervision in the Engineering Experiment Station at the University of Illinois. The accompanying sketch shows the connections used in DIELECTRIC STRENGTH OF PORCELAINS. 41 T/tMA'S. s4Af C/Zf? ^OC ^S?Z. . X/y &C/-// r / r & ! 1 1 i ts^ ■» £ 1 -*wwwwv\ the test: G is a generator of 60 kilowatts capacity which pro- duces practically a sine wave of electromotive force. T is a transformer stepping the voltage of the generator up by a four to one ratio. HT is a transformer of 10 kilowatts capacity which is designed to step from 440 up to 100,000 volts. FR is the field rheostat of the generator by means of which the high tension voltage was varied. O is a stoneware jar having a brass electrode, E, inserted through a hole in its bottom. A similar electrode, E 1 , was arranged in such a manner that it was brought in the same straight line as E and so that it could be pulled up away from E to permit of putting the porcelain sample TS between the electrodes. The first procedure was to obtain a calibration curve of the apparatus. The connection was removed from the electrode E and E 1 and a needle gap was placed across the high tension side of the transformer. With various settings of the needle gap the voltage was gradually brought up by varying FR until the discharge took place across the gap, at which time the voltage on the low tension side of the transformer was read by means of the voltmeter Ym. In this way the relation between "volts primary" and "length of the needle gap" was obtained. Then by means of the well known A. I. E. E. curve between "distance between needle points in air" and "volts," the "centimeters width of needle gap" were translated into "volts secondary." This calibration was repeated several times and good checks were obtained so the average curve between "volts primary" and "volts secondary" was adopted as the calibration curve. 42 DIELECTRIC STRENGTH OF PORCELAINS. In making the puncture tests the connection was made as shown in the diagram, a porcelain test piece, TS, was placed be- tween the electrodes and the stoneware jar O filled with trans- former oil. The voltage was gradually brought up by varying FR until puncture took place, at which time the "volts primary" were read by means of the voltmeter Ym. By means of the cali- bration the curve "volt secondary," that is, the volts to produce rupture, could be obtained. In all the tests care was taken that the rate of increase in voltage was uniform for all samples. In Mr. Minneman's discussion of this paper the question of accuracy of the results obtained is brought up. Since the cali- bration curve was obtained by reference to a needle gap it may be in error by as much as 4 per cent. Since it was made all in one day under as constant conditions of weather, etc., as possible and since several checks were made it is probable that the error in calibration is less than this. However great the error in the calibration curve is, it is a constant error and affects the reading only when considered as absolute values of voltage and does not affect the relative values obtained for the various samples. For instance, the tests upon soda feldspar vs. potash feldspar involve none of "the uncontrollable variables such as varying weather conditions, growth of charge, variation of wave form and time element," mentioned by Mr. Minneman. The values obtained for these two porcelains should be closely comparable even if the absolute values of voltage were seriously in error since the errors should be the same for both sets of tests. Mr. Minneman also mentions that "when testing a porcelain in air, after puncture takes place there is a continuous flow of current and the piece ceases to act as an insulator." This same action takes place with tests under oil. At the instant of rupture the current follows the arc and continues to follow it as long as the voltage is on in the same way as it does with a test in air. A second application of voltage in the same spot does show that there is still considerable dielectric strength after the first puncture. This dielectric strength is not, however, due to the protective effect of the oil. The current which follows the arc fuses the porcelain and when the circuit is broken the fused porce- DIELECTRIC STRENGTH OF PORCELAINS. 4,} lain solidifies in place, forming a glassy spot. Due, perhaps, to flaws and to the presence of foreign material such as carbonized oil, which probably prevents the formation of a homogeneous structure, the strength on second puncture is less than on the first. The voltage at which a sample will puncture the second time has, I believe, no relation to the real dielectric strength, i. i, on first puncture, of the porcelain sample. I believe that the only serious effect of testing under oil would be with very poorly vitrified porcelains such as are obviously not fit for high tension insulators. In testing these porous porcelains comparable results possibly would not be obtained under oil. UNIVERSITY OF ILLINOIS BULLETIN Vol. X. SEPTEMBER 16, 1912. No. 3 [Entered February 14, 1902, at Urbana, Illinois, as second-class matter under Act of Congress of July 16, 1894.] BULLETIN No. 17 DEPARTMENT OF CERAMICS A. V. BLE1NINGER, Director THE EFFECT OF ACID5 AND ALKALIES UPON CLAY IN THE PLASTIC STATE BY A. V. BLLININGLR AND C. E. FULTON NOTE ON THE DISSOCIATION OF CALCIUM HYDRATE BY R. K. HURSH NOTE ON THE RELATION BETWEEN PREHEAT- ING TEMPERATURE AND VOLUME SHRINKAGE BY R. K. HURSH 1911-1912 PUBLISHED FORTNIGHTLY BY THL UNIVERSITY [Reprinted from Transactions American Ceramic Society, Vol. XIV, by Permission.] THE EFFECT OF ACIDS AND ALKALIES UPON CLAY IN THE PLASTIC STATE. A. V. Bleininger and C. E. Fulton, Urbana, 111. INTRODUCTION. The effect of acids, alkalies and salts upon clay suspensions (slips) has been discussed frequently, and the work of Simonis, Mellor, Rieke, Boettcher, Ashley, Foerster and Bollenbach deals with the viscosity and other phenomena of systems in this state. But little is known concerning the effect of such reagents upon clays in the plastic condition which differs from that of a sus- pension, due to the cohesive influence of the particles upon each other. It has been realized for some time that the properties of clays in the wet state are influenced by the presence of alkalies and acids. Seger explains the increase in the plasticity of clay upon storing by the assumption that the fermentation of organic sub- stances results in acids which neutralize the alkalinity due to the decomposed feldspar, and in addition bring about the "sour" condition which accompanies the improvement in working qualities. Rohland 1 discusses this subject from the theoretical standpoint and makes quite definite statements with reference to the principles underlying the effect of various reagents upon clays in the plastic state. He arrives at the conclusion that the plasticity of clays is increased by the presence of H + ions, while, on the other hand, the OH' ions are active in the opposite direc- tion. According to Rohland, the plasticity is likewise increased by the addition of colloids like tannin, dextrine, etc., as has been shown by the work of Acheson, fine grinding and the storage of the clay in cool and moist places. It is supposed that the in- crease in plasticity is coincident with the coagulation which is primarily due to the presence of the hydrogen ions; it is retarded by the hydroxyl ions. The salts of strong bases and weak acids which dissociate OH' ions hydrolytically produce an effect similar to that of the hydroxyl ions. Neutral salts, Rohland goes on to say, with but few exceptions, are indifferent in their 1 "Die Tone," pp. 35-19. 4 EFFECT OF ACIDS AND ALKALIES UPON CLAY. effect, though some appear to show a contradictory behavior, which has not yet been explained. "The effect of the hydroxyl ions may be weakened, compensated or strengthened by the action of the salt in question. Thus borax is an example of the first class and sodium carbonate of the second." The same writer further says that with some clays the addi- tion of Na 2 C0 3 brings about an improvement in plasticity, while ordinarily the same reagent behaves in the opposite sense, due to the hydrolytic dissociation of OH' ions. It is possible that the effect of hydroxyl ions might be neutralized by the C0 3 " ions. DRYING SHRINKAGE. A decided lack of data exists with reference to the deter- mination of the effect of reagents upon the plasticity of clays. It was thought advisable for this reason to begin work along this line without reference to any theoretical speculations. The most obvious criterion to be used in this connection is the drying shrinkage, which, from what we know of the properties of clays, is a function of plasticity. It is evident that any effect caused by the addition of reagents will at once be indicated by the shrinkage of the clay. In this series of experiments Georgia kaolin was used. This clay was found to show an acid reaction when tested with phenol- phthalein. This would indicate that the addition of acid should bring about no decided change in the clay, a fact which was verified by experiment. The reagents employed were HC1, H 2 S0 4 , NaOH and Na 2 C0 3 . In carrying out the work a thoroughly mixed sample was first prepared so that variations due to differences in composition were reduced to a minimum. The test specimens were in the shape of bars 3 5 / 16 x i x 5 / 8 inches. Even the most careful linear shrinkage measurements by means of the vernier caliper were found to be unsuitable for the work. A volumenometer permitting of readings to 0.05 cc. was then employed. The measuring liquid used was petroleum from which the lighter oils had been expelled by heating. The bars were at once weighed and allowed to dry at the laboratory temperature for three days, after which they were heated at no° to constant EFFECT OF ACIDS AND ALKALIES UPON CLAY. 5 weight, and their shrinkage determined. For each concentration of reagent three bars were made and measured. Clay and Water. — A study was first made of the drying shrinkage of the clay with different amounts of water, ranging from the soft state in which the clay could be barely molded to the condition of minimum water content when molding was likewise difficult for the opposite reason. The shrinkage rela- tions to the various contents of water are shown in Fig. i. The third point on the curve, showing a shrinkage of 10.45 P er cent, with a water content of 32.8 per cent., represents the most work- able state. Any increase in water above this point is at once ob- served by the rapid softening of the mass. The clay hence is well suited for the work at hand, owing to the ease with which the condition of best working behavior is recognized in distinction from many other plastic clays which possess a long working range. Effect of Acid. — Upon adding from 0.025 to 0.525 gram of hy- drochloric acid to 100 grams of clay, we observe from Fig. 2 that the shrinkage is not materially affected by this reagent. While two maxima of somewhat greater contraction are noted, the principal result seems to be a reduction in shrinkage, contrary to what might be expected from Rohland's statements. The fact re- mains, however, that conditions are more complex than they seem, due to the probable solution of various salts in the clay as well as the formation of some chlorides by the acid. It was thought that further insight into the effect of the acid might be obtained by calculating the total and the shrinkage water in terms of the true clay volume, i. c, weight divided by the density of the powdered substance, according to the rela- tion : 100 Qt — v 2 ) w — per cent, (by volume) shrinkage water. ~d Where v t = volume of wet brickette, v 2 = volume of dry brickette, w = weight of brickette, dried at no° C, d = density of the dry and powdered clay. EFFECT OF ACIDS AND ALKALIES UPON CLAY. T&AA/S. AM Ce/? SOC kVL X/^ 0l£~//V//V6£/?&^t/i TO/V F~/G.S t.„ X a ao& art o.e2£ #.x> ajva^s as&f EFFECT OF ACIDS AND ALKALIES UPON CLAY. r/frlA'S >?/H ' C^/? \50C r&£ .x/r / ftTferj!!^ A / j/*/?//v/r. ItfiT *VA7 EW a &2>&1--* &&&^4 f^ CC - 'tTf t*v/ftt?C f//ce \ /^?/r5£- /K^r£-/f I a OATS a./s 0 &&&n»?ra &fc/£ x/f 0/.&W//V&&? /*/j!>!e?/K: cAgsjv/M££// 'M^&Z? &SZ7/773 a/~/Vi7 e c : -Z ols/ n*s/a>A?f X -• - C&/7&/&/7/ 'n'e&/7f'£>/3X7//7 n n° < >o / u 6- ' c ) °/ ft J 5 /+ 3 > r < 1 c > + + + 760 280.5 92 \ I 1 I *\ k I "Jisa 4&& ^so -jr&c? ^F0 Bulletin No. 7, Bureau of .Standards. 7 Ztschr. phys. Chem., LXII, p. 330. 20 NOTE ON DISSOCIATION OF CALCIUM HYDRATE. was heated before passing to the furnace to prevent any conden- sation. The temperature of the water in the Liebig bulb was regulated by immersing it in a water bath. The furnace was held at constant temperature, and the vapor tension maintained at a definite value for 10 minutes by regulation of the water bath temperature. The crucible was then removed from the furnace and weighed on a very fine balance. Conditions of tem- perature and vapor pressure were so regulated that the substance maintained constant weight or gained slightly during the period, and these values were taken as the corresponding temperature and dissociation pressure of the material. The results of this method for Ca(OH) 2 are shown in Fig. i. This method was found to be too slow and to frequently give inconsistent results. It was impossible to prevent the ab- sorption of some CO, while removing the crucible from the fur- nace for weighing. STATIC METHOD. Dr. Johnston then resorted to the "static method," in which the dissociation pressures are measured directly. A diagram of the apparatus is shown in Fig. 2. A platinum tube, P, about 5 cm. long and 4 mm. inside diameter, contained the substance. This tube was placed in a small electric furnace with a thermo- couple for determining the temperatures. A piece of glass tube, C, was fused to P and to one arm of a U tube which was connected to the barometer. On each arm of the U tube was a bulb, D, bent to the side and holding enough mercury to fill the U-tube to a depth of about 3 cm. To prevent condensation of the vapor from P, the U-tube and C were enclosed by a glass steam jacket. With the mercury in bulb L, the apparatus was exhausted through A by means of a mercury pump. Cock A was then closed, and the mercury run from L into the U-tube by tilting the ap- paratus. Heating was begun, and at the first indication of pres- sure in P, the mercury in the two arms of the U-tube was brought to the same level by admitting some air at B and adjusting by means of the leveling tube R. In his work with calcium hydroxide, Dr. Johnston slaked pure CaO and absorbed the excess water in a desiccator. An- other portion was made by allowing the CaO to absorb moisture XOTE ON DISSOCIATION OF CALCIUM HYDRATE. rfZ4ws. ^m. c£~/?. sac. /^?z. x/y /Jt/tt/-/ 21 slowly until the composition was about CaO o.8H,0. In using this substance, it was found necessary to heat it slightly during exhaustion of the apparatus since pressures of several cm. ap- peared between 200 ° and 300 ° which again disappeared in part on further heating. These abnormal pressures were supposedly due to loosely combined or absorbed moisture, and upon their appearance the test was stopped and the apparatus again ex- hausted. Only such pressures were taken as appeared at definite temperatures on heating and again disappeared on cooling. The "abnormal pressures" disappeared only partly on cooling. Un- der these conditions, it was found advisable to use a mixture of CaO and the hydroxide, although this did not entirely eliminate 22 NOTE ON DISSOCIATION OF CALCIUM HYDRATE. the trouble, which was noted with all of the hydroxides studied. The results of the work on Ca(OH) 2 by this method are shown in Fig. 3. By the curve, it is seen that the dissociation pressure 1 I r/?s?-4/K5 AA*.££rt.SOC. Vai.je/V /=/& ^r *-/ts/?SH r 36.SS % 1 $ %3C X ess % J * //. 46% &OO J00 6OO The results of these experiments indicate the existence of two hydrates of CaO, the CaO.H 2 dissociating at 375 ° C, leav- ing a lower hydrate which dissociates at 580 C, leaving CaO. That the loss of weight at each point is due to the dissociation of a chemical compound is shown by the shape of the curves. The break is abrupt with no gradual slope preceding it. If me- chanical or dissolved water were being driven off, there would be a gradual loss of weight with increasing temperature. SUMMARY. Various temperatures are given for the dissociation of Ca(OH) 2 ranging from 450 ° by Le Chatelier to 547 ° C. by Johnston. NOTE OX DISSOCIATION- I >F CALCIUM HYDRATE. 25 Using the "loss of weight" method, two dissociation points are found. The hydrate, Ca(OH) 2 , dissociates at 375 °, forming a lower hydrate that loses its H,6 at 580 C. No mechanical water was driven off above 25 ° C. In conclusion, the writer wishes to express his indebtedness to Professor A. Y. Bleininger for many valued suggestions in this work. [Reprinted from Transactions American Ceramic Society, Vol. XIV, by Permission.] NOTE ON THE RELATION BETWEEN PREHEATING TEM- PERATURE AND VOLUME SHRINKAGE. By R. K. Hursh. INTRODUCTION. An extended study of the effect of preliminary heat treat- ment upon clays within a practical temperature range has been made by Professor Bleininger. 1 Especial attention was given to the effect upon the volume shrinkage. A decided change in the properties of most of the clays was noted at temperatures of 200 ° to 300 ° C. They became more or less granular and decreased markedly in plasticity. There was a material decrease in the volume shrinkage and an increase in the amount of pore water. In a few cases, this change occurred at somewhat higher tempera- tures. One fine-grained, highly plastic clay, similar in behavior to bentonite, showed a considerable change in physical proper- ties at 250 ; but treatment at temperatures up to 400 ° failed to reduce the shrinkage to working limits. Professor Or ton, 2 in studying some tertiary clays which gave trouble in drying, found ordinary preheating temperatures to be ineffective. When the temperature was raised to 450°-5io° C. the plasticity and shrinkage were reduced sufficiently to make the clay workable. Under the conditions of the tests the period of safe treatment at these temperatures was closely limited since the clays lost their plasticity entirely when kept a little too long in the dryer. As some time is required for heat to penetrate the clay it is possible that the temperature may have reached a higher point in the longer treatments than was indicated by the thermo-couple. The test, however, represents the prac- tical conditions in a rotary dryer. EXPERIMENTAL WORK. The present work was undertaken with the purpose of se- curing some further data upon the effect of the higher tempera- tures of preheating upon the physical properties of clays as in- dicated by changes in volume shrinkage. Four clays were used: 1 Bull. No. 7, Bureau of Standards. 2 Trans. A. C. S.. Vol. XIII, p. 765. 2S PREHEATING TEMPERATURE AND VOLUME SHRINKAGE. /O0 £00 J00 400 ^~00 <500 ^r&/?e0/ys& 7es77/p. -°c 4Vr /=/&£. If 80 /&■ >4*- /o ""* — , / ^^ w pj H ^o-_ ™ ■ 1 — =; »■— . — "* H H i — < ^- u ^ T" N 1 — ' k >j>' /!•' BORIC ACID-SILICA MIXTURES. 5 /oak 906 800 7<% T/?A/VS.AMC£/?.SOC. WLX/f /^/O. / &LE/W/MO£ff& TEETO/? ^tvo ^00 <&oo 30W- O 0.2 0.4- 0.6 0.3 /.O /.e /.4 /.6 /.ff £0 MOLECULES 0ES/0 2 6 A THERMAL STUDY OF BORIC ACID-SILICA MIXTURES. In going over this part of the work four times, the results shown in Fig. i were obtained. The softening points of the mixtures beyond B 2 3 .2Si0 2 are not plotted since the divergence in this part of the series is still greater. Softening point determinations were also made upon rods drawn from all of the fusions but these likewise gave extremely variable results, considerably lower than those obtained for the cones. The evidence thus far collected makes it apparent that any reaction taking place under these conditions would be greatly hindered by the internal molecular friction. HEATING AND COOLING CURVES. A considerable number of heating and cooling curves were determined with special reference to the B 2 3 .2Si0 2 mixture. The latter was prepared from fused B 2 3 and prepared Si0 2 , and from fused boric acid and flint, passed through the 200 mesh sieve. In no instance was there a temperature acceleration or lag observed, and, hence, the observation of Binns was not checked. In Fig. 2, the heating curve in which the couple readings were made by means of a potentiometer indicator is shown. The junction was kept at o°C. by means of ice. In Figs. 3 and 4, both the heating and cooling curves for prepared silica and flint mixtures as indicated by a Siemens and Halske recorder, making a contact every 16 seconds, are presented. It was observed that on fusing any mixture of B 2 3 and Si0 2 , without previous fritting, some vapor was expelled suddenly, carrying evidently a certain amount of boron. This happened also when both the boric acid and silica had been ignited separately to constant weight before mixing. Since Professor Binns used an optical pyrometer, it is quite possible that by focusing upon this vapor the readings were changed as observed by him. SOLUBILITY DETERMINATIONS. The different mixtures were fused and pulverized on cooling. The resulting powder was screened through the 80 and 150 mesh sieve. All material coarser than the 80 and finer than the 150 mesh was rejected. One gram samples were then weighed and put in stoppered 250 cc. Erlenmeyer flasks. These were placed A THERMAL STUDY OF BORIC ACID-SII.ICA MIXTURES. 7 rfrW /K5>7 MC£ tr^so r.^?z .x/v E/c 7. a &l.£/A///VGEf?& T££rO/? M/Xr£ US/A/G fVr£AT/0M£T£/? /?£CO/?C£/? /o ^0 -30 40 T-/A<& r£ETO/9 0.2 0.4- ae off /.o /.a /.R CAST [RON. 1 5 of the trial. The holder for the trial piece consisted of a bar of iron "upset" at one end and so shaped as to fit on the inside of the trial piece. Series I. REPLACEMENT OF TIN OXIDE BY ANTIMONY OXIDE IN A TIN ENAMEL. This series was carried out by replacing the tin oxide in an enamel similar to that given by Riddle in his "Types of Enamels for Enameling Cast Iron Sanitary Ware," Trans. A. C. S., Vol. IX, with antimony oxide, thus: 0.25 Na 2 o. 10 MgO 0.15 PbO 0.15 BaO 0.15 K 2 0.05 ZnO 0.15 CaO Batch formulae (in equivalents). 0.15 A1 2 3 ] i.ooSiO, o . 20 B,0 3 J o . 1 5 vSn0 2 -o . 075 Sb 2 3 No. O u a ■0 CJ d pq fa O O a N O O M u pa a to E c to 0.15 0.15 0.15 0.15 0.15 0.05 0.05 0.05 0.05 0.05 0.15 0.15 0.15 0.15 0.15 O.I5 O.I5 O.I5 O.I5 O.I5 O.O5 O.05 O.O5 O.O5 O.05 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0.15 0.15 0.15 0.15 0.15 0. 10 0. 10 0. 10 0. 10 . 10 0.15 0. 1125 0.075 0.0375 0.00 O Ol88 3 4 5 0-0375 O.O56 O.075 Description of Trials.^ — No. i is a good enamel and is a typical tin enamel. All of the rest of the series, with the possible exception of No. 2, are very poor. A peculiar "puckery" or matte texture exists, the surface is rough and uneven, and the enamel flies off in patches, resembling shivering of clay ware. In the trials of enamels 3 and 4, the "puckery" effect is partially overcome by laising the burning temperature. The shivering is also lessened by this treatment. It is also evident in this series as well as in the rest of the work that where an enamel is applied, too thick shivering is more likely to occur. Thinking perhaps that the "puckery" effect might be over- come partially by making a more easily fusible enamel it was 1 6 REPLACEMENT OF TIN OXIDE IN ENAMELS FOR CAST IRON. decided to run a series with a more fusible RO combination. It was also suggested that the "puckery" effect might be due to the barium which reacted with the sulphur present in the Sb 2 3 . 7 Some of the Sb 2 3 was tested and found to contain sulphur. A series embodying the two above ideas was accordingly carried out as given below. Although it was not conducted strictly on a scientific basis it is sufficient to show in a practical way the desired effect. Series II. VARIATION OF BARIUM OXIDE AND ITS EFFECT ON ANTIMONY OXIDE. 0.25-0.54 Na 2 o. 10-0.00 MgO o. 15-0'. 15 PbO o. 15-0. 16 K 2 0.05-0.05 ZnO o. 15-0. 10 CaO o. 15-0.00 BaO o. 15-0. 16 Al 2 O s o. 20 B 9 0, 1 .00 Si0 2 0.075 Sb 2 3 Batch formulae (in equivalents). 6 13 V u a as O O a N O •z M +J "o >> u K O Bi O X CS Ih pq O u at 1-1 as » 3 I 2 3 4 O.15 O.21 O.29 0-35 0.05 0.05 0.05 0.05 0.15 0. 10 0.05 0.00 O.15 O. IO O.05 O.OO 0.05 0.05 0.05 0.05 0.00 0.02 0.04 0.06 0.00 0.02 0.04 0.06 O.OO O.O3 O.O7 O. IO 0. 10 0. 10 0. 10 0. 10 0. IO 0.07 0.03 0.00 O.I5 O. 148 O.136 O.13 0. 10 0.14 0.18 0.22 0.075 0.075 0.075 0.075 Description of Trials. — The "puckery" effect has decreased toward the end of the series which contains no barium and in No. 4 is not present at all. This enamel is a fair enamel which adheres well. No. 1 is somewhat shivered. This series shows from a practical standpoint that barium should not be used to any very large extent in an enamel where there is a contact with sulphur gases. Its use, however, in enamels where tin is used as an opacifier is very much desired, owing to its ability to decrease shivering. 7 Sb 2 3 is prepared from stibnite, SD2S3, by roasting in air, hence sulphates are formed which, if not entirely removed, would combine with the barium compounds. REPLACEMENT OF TIN OXIDE IX ENAMELS POS CAST IRON. 1 7 Series III. VARIATION OF THE SILICA CONTEXT. This series was varied between the limits of 1.00 and 2.00 •equivalents of silica as shown : o. 10 CaO o . 54 Na 2 0.15 PbO o.i6K,0 0.05 ZnO 0.16 ALA, 0.20 BX), 1 .00-2 .00 SiO, 0.075 Sb 2 3 Batch formulae (in equivalents). O S S3 ■d 3 V pi O a N O V "3 >> H u x 3 S a n a a JS 2 3 4 5 6 7 8 9 o-35 0-35 o-35 o.35 o.35 o-35 o-35 o-35 o-35 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 O.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.22 o.345 0.47 o.595 0.72 0.845 o.97 1 095 1 . 22 0.075 0.075 0.075 0075 0075 0.075 0.075 0.075 0.075 Description of Trials. — Nos. 1, 2 and 3 have an egg shell- like texture but otherwise are fair enamels. The trials of enamels Nos. 4 and 5 are better and do not show the above texture to such a degree. No. 6 is a fair enamel but is a trifle dull. No. 7 is a good enamel and adheres well. It is whiter and has a better gloss than the average commercial enamel. Enamel No. 8 is whiter than No. 7 and has a better gloss. A few of the trials shiver somewhat, showing that the silica is a trifle too high. Enamel No. 9 has shivered still more, but on the trials where it held, it is the whitest and most brilliant of the series. Enamels Nos. 8 and 9 have an exceptionally white color and are more than the equal of the average tin enamel in this respect. The result of this series seems to show that the last two enamels are too high in silica and also that a silica content of over 1.85 equivalents is conducive in shivering. The burning temperature rises as the silica content increases; but this heat, 1 8 REPLACEMENT OF TIN OXIDE IN ENAMELS FOR CAST IRON. even with the enamels containing 2.0 Si0 2 , did not cause the iron to deteriorate to any visible extent. As silica increases, the whiteness is increased, and it is evident that a sacrifice must be made of part of the whiteness in order to obtain enamels that do not shiver. Series IV. VARIATION OF ALUMINA. This series was run between the limits of 0.1 and 0.2 equiv- alent of A1 2 3 . To bring in the A1 2 3 in combined form, i. e., as spar, it was necessary to change the RO with respect to K 2 and Na,0 thus: o . 1 6-0 . 20 K 2 0.15 PbO o . 10 CaO o . 54-0 . 50 Na 2 0.05 ZnO o . 10-0 . 20 ALO, I 1 . 80 SiO, 0.20 B,0, 0.075 Sb 2 3 Batch formulae (in equivalents). 6 O u •0 ca a .J O a N M >, u u X O a X a u pq u a a M ■!-> a d 1. . . . 2. . . . 3 4 5 6 o-35 0.342 0-334 0.326 0.318 0.31 O.05 O.05 O.05 O.05 O.05 O.05 O.O5 O.O5 O.O5 O.O5 O.O5 O.O5 0.06 0.049 0.038 0.025 0.013 0.00 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 O.IO O.IO 0.16 O.IO O.IO O.IO O.IO O.IO O.IO O.IO O.IO O.IO 0.07 0.09 O.I I 0.13 0.15 0.17 1.38 1.26 1. 14 1.02 0.90 0.78 0.075 O.O75 O.O75 O.O75 O.O75 O.O75 Description of Trials. — All enamels of the series are good enamels with whiteness increasing toward No. 6, i. e., with in- crease of A1 2 3 . The temperature required for maturing increases, however, with the A1 2 3 . The best enamel of the series, taking burning temperature, whiteness, gloss, and adhesive properties into consideration, is No. 4 containing 0.16 A1 2 3 . Series V. VARIATION OF ANTIMONY OXIDE. This series as well as the remaining two series was carried out in two parts, A and B, the two parts being practically alike REPLACEMENT OF TIN OXIDE IN ENAMELS F( >K CAST [RON. I 9 -except for the silica content. Part B was carried out first and the limits of Sb 2 3 were not high enough, hence these were changed in A. Series V, A. o.i6K,0 ] 0.05 ZnO 0.16AUO3 ] i.8Si0 2 o.ioCaO \ o.isPbO |o.2oB,0 3 Jo-o.i4Sb 2 3 o . 54 Na 2 J Series V, B. I6K 2 1 05 ZnO 10 CaO 15 PbO 54 Na 2 J 0.16 A1,0, o . 20 B,0 :f 2.0 SiO, o -o . 1 1 Sb 2 0.., V, A. Batch formulae (in equivalents). 6 S3 O u •0 a pi C a N to "0 u X rt a Borax K. Spar s W I 2 3 4 5 6 7 8 0-35 0-35 o-35 o.35 o.35 0.35 o-35 0.35 O.O5 O.05 0.05 0.05 O.05 O.05 0.05 O.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 0. 10 O. IO O. IO O. IO O. IO O. IO O. IO O. IO O. IO O.I3 O.I3 O.I3 O.I3 O.I3 O.I3 O.I3 O.13 1 .02 I .02 1 .02 1 .02 1 .02 1 .02 1 .02 1 .02 O.OO 0.02 O.04 O.06 O.08 O. IO 0.12 0. 14 V, B. Batch formulae (in equivalents). to 1 0.35 2 o-35 3 0-35 4 0.35 5 o-35 6 0.35 <& N U a 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 o. 10 O. IO O. IO O. IO O. IO O. IO O. IO O. IO O. IO O. IO O. IO O. IO 0.13 0.13 0.13 0.13 0.13 0.13 0.00 0.022 0.044 0.066 0.088 O. I I Description of Trials. — The trials of enamel 1 A have but 20 REPLACEMENT OF TIN OXIDE IN ENAMELS FOR CAST IRON. slight opacity. No. 2 A has a trifle more and so on up the series. Enamel No. 3 A has a fair opacity, No. 4 A and 5 A are good enamels, No. 5 A being the whitest. No. 6 A is a good enamel. It is whiter than No. 5 but is not quite so glossy. No. 7 is a good enamel and is a trifle "matte" in texture. No. 8 has a beautiful matte texture and differs from all the rest of the series in this respect. One of the trials, however, shows a tendency to shiver but this may possibly be due to the mode of application. Enamel No. 5 is the best of the A part of the series, taking gloss, finish, and general appearance into consideration, while for a dull or matte texture No. 8 is the best. Enamels No. 7 and 8 require a higher temperature for burning, thus indicating that high antimony decreases the fusibility. With part B of the series shivering is more evident in every case. The enamels which held are, however, of greater brilliancy and opacity, enamel No. 2 of A being identical in appearance with No. 1 of B. Enamels 2, 3 and 4 of part B are practically the same as 3, 4 and 5 of part A respectively. From this we would conclude that 0.016 equivalent of Sb 2 3 , in this range of silica content, has about the same opacifying effect as 0.02 equivalent of silica. Series VI. REPLACEMENT OF ANTIMONY OXIDE BY TIN OXIDE IN AN ANTIMONY ENAMEL. This series, also using two different equivalents of silica, , was carried out as follows: VI, A. 0.16 K 2 ] o.o5ZnO I0.16AUO3 ] i.8oSi0 2 o. 10 CaO 0.15 PbO I 0.20 B.,0 3 J 0.075 Sb.5O3-o.15 SnO., o . 54 Na,0 J VI, B. 0.16 K 2 ] 0.05 ZnO | 0.16 A1,0. ; ] 2.0 Si0 2 0. 10 CaO f r 0.15 PbO 1 0.20 B 2 0, J 0.075 Sb„0 3 -o.i5 SnO. . 54 Na 2 J REPLACEMENT OF TIN OXIDE IN ENAMELS FOR CAST [RON. 21 Hatch formulae (in equivalents). VI, A d -' 3 N 5 c 3 M CO E : : c I. . . . 0.35 0.05 O.O5 0.03 O.O6 O.IO O.IO 0.13 1.02 0.075 0.00 j. . . . 035 0.05 O.O5 0.03 O.06 O.IO O.IO 0.13 [.02 0.056 0.038 3- ■• • 0-35 0.05 O.O5 0.03 O.06 O.IO O.IO 0.13 1.02 0.038 0.075 4 0.35 0.05 O.O5 0.03 O.06 O.IO O.IO 0.13 I .()_• 0.019 O.] 125 5... . 0.35 0.05 O.O5 0.0;, 0.06 O.IO O.IO 0.13 1.02 0.00 O.15 VI, B. I. ... . o.35 0.05 0.05 0.03 0.06 O.IO O.IO 0.13 [.22 O.O75 O.OO 2. . . . o.35 0.05 0.05 0.03 0.06 O.IO O.IO 0.13 1.22 O.O56 O.O38 3 o-35 0.05 0.05 0.03 0.06 O.IO O.IO 0.13 [.22 O.O38 O.O75 .1 o-35 0.05 0.05 0.03 0.06 O.IO O.IO 0.13 1.22 O.OI9 O.II25 5 o.35 0.05 0.05 0.03 0.06 O.IO O.IO 0.13 [.22 O.OO O.I5 Description of Trials. — All enamels of the A part of the series adhere tenaciously and are good enamels. Enamel No. 1 has more opacity and whiteness than Xo. 5, these two properties decreasing uniformly between these extremes. The antimony enamel requires a slightly higher temperature for maturing, but not to such extent as to be detrimental to the iron. In the B part of the series shivering is much in evidence, due to the increased silica. Enamels Nos. 1 and 2 have good opacity but Nos. 3 and 4 are much inferior in this respect. In enamel No. 5 the silica has dissolved the Sn0 2 almost entirely. Taking the results of this series we would conclude that Si0 2 at the higher limit is opposite in effect with regard to Sb a O a and SnO,. In the case of Sb,0 3 the opacity, whiteness and brilliancy are increased, while with Sn0 2 these properties, notably the opacity, are decreased. Shivering, however, is increased in either case. The results obtained in part A of the series are not in accord with those of Riddle whose high limit of silica was 1.25 equivalents. In enamel No. 5 part A as given above, a good white enamel was obtained using i.S equivalents of silica. It might be interesting to note also at this point, the be- havior of the enamels on wrought iron. The- enamels of part A were applied to iron washers, and although they had not been 2 2 REPLACEMENT OF TIN OXIDE IN ENAMELS FOR CAST IRON. previously cleaned, the enamels held perfectly and were of good whiteness, brilliancy and texture. Series VII. VARIATION OF BORIC OXIDE. This series employs two equivalents of silica and the Na 2 C0 3 content is varied in order to reach the lower limit of B 2 3 still maintaining the same ratio. VII, A. 0.16 K 2 ] 0.05 ZnO J 0.16 A1 2 3 o. 10 CaO 0.15 PbO o . 54 Na 2 o. 10-0.40 B 2 3 J 0.075 Sb 2 3 VII, B. ] 2 . 00 SiO., 0.16 K 2 0.05 ZnO J 0.16 A1 2 3 o. 10 CaO \ 0.15 PbO I o . 10-0 . 40 B 2 3 J 0.075 Sb 2 3 0.54 Na 2 J VII, A. Batch formulae (in equivalents) Z O ■a h-1 pi O e K O u ■3 u O U Borax K. Spar ft 7; 1 0.4 o-375 0.350 0-325 0.300 0-275 0.25 O.O5 O.O5 O.05 O.O5 O.05 O.O5 O.O5 O.O5 O.O5 O.O5 O.O5 O.O5 O.O5 O.O5 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.06 0.06 0.06 0.06 0.06 0.06 0.06 O.IO O.IO O.IO O.IO O.IO O.IO O.IO O.05 O.075 O.IO 0.125 0.150 0.175 0.2 0.13 0.13 0.13 0.13 0.13 0.13 0.13 1.02 1.02 1.02 1.02 1.02 1.02 1.02 0.075 0.075 0.075 0.075 0.075 0075 0.075 3 4 5 6 7 VII, B. 0.4 0.05 0.05 0.03. 0.06 O.IO 0.05 0.13 1.22 0.375 0.05 0.05 0.03 0.06 O.IO 0.075 0.13 1.22 0.350 0.05 0.05 0.03 0.06 O.IO O.IO 0.13 1.22 0.325 0.05 0.05 0.03 0.06 O.IO 0.125 0.13 1.22 0.300 0.05 0.05 0.03 0.06 O.IO 0.150 0.13 1.22 0.275 0.05 0.05 0.03 0.06 O.IO 0.175 0.13 1.22 0.250 0.05 0.05 1 0.03 0.06 O.IO 0.200 0.13 1.22 0.075 0.075 0.075 0.075 0.075 0.075 0.075 REPLACEMENT OF TIN OXIDE IN BNAMBLS POR CAM [RON. 23 Description of Trials. — All enamels of part A adhere will and are good white enamels up to No. 6. Nos. 6 and 7 have a yellowish east and are not all desirable enamels. Bubbling is also evident in the enamels of higher B,0 3 content. Enamel No. 1 is the whitest of the five enamels. The results obtained in part B are substantially the same as those of part A. The enamels are whiter, however, than the ones of the same B 2 3 content and the yellowish cast of enamels 6 and 7 of part A has disappeared in the corresponding enamck of part B. Shivering is present to quite a large extent in part B, due to the high silica. As in part A, bubbling is prominent in the enamels of the higher B 2 3 content. The difference in whiteness of the high and low B,0 3 enamels in part A is not so pronounced in this part of the series. Enamels B 1 and B 7 have very little difference in whiteness, B 1 being a little the whitest. The difference in maturing temperature is however quite large and the tendency to bubbling is more evident. The results indicate that the lower the B 2 3 the better and whiter are the enamels. The limits for desirable enamels are about 0.15-0.30 B 2 3 . LIMITS OF THE INGREDIENTS. The limits of the ingredients and their effects established by this work are as follows: Si0 2 : The effect of silica is to increase brilliancy, white- ness, acid-resisting properties and gloss. If increased too high, shivering takes place and the maturing temperature is too high. The limits are about 1. 65-1. 85 equivalents, those nearer the higher limit being the preferable. A1 2 3 : Increased A1,0 3 increases the temperature for matur- ing and gives whiter enamels. The high limit is around 0.1S equivalent. The low limit was not established but for com- mercial enamels is probably about 0.13 equivalent. Sb 3 : The effect of Sb 2 3 is to increase the maturing tem- perature, and to increase the whiteness and opacity when em- ployed between the limits of 0.0-0.09 equivalent Sb 2 O s . If used between the limits of 0.1-0. 14 equivalent the enamels are dull at the lower limits and matteness increases at the higher. 24 REPLACEMENT OF TIX OXIDE IN ENAMELS FOR CAST IRON. At the high limit, 0.14 equivalent, shivering is likely to occur. For brilliant enamels of good opacity and texture the limits are 0.06-0.09 equivalent, about 0.075 being preferable. SnO., : No variation of the Sn0 2 content was made but a good enamel was obtained using 0.15 equivalent of Sn0 2 . B„0 3 : The effect of increased B 2 3 is to lower the maturing temperature, to increase the tendency to produce bubbles, to decrease the whiteness when used above a certain limit, increase gloss, and to increase the solubility of the enamel. The limits are about 0.15-0.3 equivalent, those nearer the lower limit being preferable. BaO: The effect of BaO in Sb 2 3 enamels is to produce a "puckery" or matte effect. This is no doubt due to the sulphur arising from the Sb 2 3 and the fuel gases, which comes in contact with the barium compounds. The most likely enamel taking all points into consideration is: o.i6K,0 ] 0.05 ZnO I o. 16 A1.,0 3 J 1 .80 SiO a o . 10 CaO \ 0.15 PbO j 0.20BA J0.075Sb.P3 o.54 NaX> J DISCUSSION. Professor Stale y: Why do you not include the fluorine in your formula? No one will be able to calculate the batch from the formula unless you do so. Moreover, it makes a vast differ- ence whether an enamel contains a small or a large amount of this element. Mr. Brown: I do not think it is necessary. I introduced it as cryolite, using 0.06 equivalent of cryolite throughout. Professor Staley: Mr. Brown, I just want to ask one more question. Did you get an absolutely pure white enamel, or was it of a greenish or bluish tint? There have been many attempts made to use antimony in place of tin oxide in cast iron enamels, but it has never given a satisfactory white. They get a tint they call white, but it is not a commercial white. Do you have any idea of how to avoid getting that greenish, bluish white so characteristic of antimonv oxide? REPLACEMENT OF TIN OXIDE IN I-NAMI-I.S POR CAST [RON. 25 Mr. Brown: I did not carry on work to eliminate the cast you speak of. The cast was not present to an aggravated extent that I could see. A number of others said the same thing. There is a slight bluish cast or tint in some of the trials Professor Sialey; In your final enamel as well as in all the others? Mr. Brown: It was not so pronounced in this case, but more so in the enamels of higher silica content. Mr. Hurt: I noticed in speaking of the enameled iron industry they always speak of dusting the enamel on and I would like to get a little description of what the mechanical process is — of what is involved in this dusting on of the glaze. Professor Staley: In a paper ("The Manufacture of Enameled Iron Sanitary Ware," Trans. A. C. S., Vol. VIII, p. 172) I pub- lished several years ago, you can find a description of the ordinary method of making a piece of enameled cast iron. The only difference between the method described there and the method used at present is the use of a mechanical agitator. Mr. Burt: What mesh sieve do you use? Professor Staley: The sieve is a fifty- or sixty-mesh sieve. Mr. Brown: I would like to ask Professor Staley what his opinion is of the fluorine in a fused enamel — whether it is volatilized or whether it is retained in the enamel. I have read of several instances where they analyzed for fluorine and found it in the enamels in small quantities. Professor Staley: That is all a matter, in my mind, of how- hard, how long, and how hot you heat the enamel. You can volatilize it all, 01 you can have the larger portion of it stay in. If it is all volatilized you have no opacifying effect from the use of fluorides. In cast iron enamels that are heated or fritted in the ordinary length of time, the large bulk of fluorine stays in. NOTE PREPARED AFTER READING THE PAPER. Professor Bleininger: It seems to me that Mr. Brown has solved his problem satisfactorily. He has accomplished two things, viz., the production of a white enamel which compares favorably with the best tin enamels, in the opinion of impartial observers, and he likewise has shown clearly the kind of enamel 26 REPLACEMENT OF TIN OXIDE IN ENAMELS FOR CAST IRON. required for the use of antimony as an opacifier, which differs somewhat from the common type. As regards the poisonous quality of antimony compounds. Rickmann, Sprechsaal, XLV, 115-117, says that during an ex- perience of ten years the use of metasodium antimonate has not proven injurious. However, he points out that the antimony oxide compounds (tartar emetic, etc.) are poisonous. For cast iron enamels, therefore, the use of Na 2 Sb 2 3 might be a perfectly feasible solution. UNIVERSITY OF ILLINOIS BULLETIN ISSUED WEEKLY Vol. XI. MAY 11. 1914. No. 37 [Entered as second-class matter December 11, 1912, at the post office at Urbana, Illinois, under the Act of August 24, 1912.] BULLETIN No. 19 DEPARTMENT OF CERAMICS R. T. STULL, Acting Director INVESTIGATION ON IRON ORE CEMENTS BY ARTHUR .E. WILLIAMS PUBLISHED BY THE UNIVERSITY OF ILLINOIS, URBANA 19 13-1914 Authorised Reprint from the Copyrighted Proceedings Volume VIII, 1912. NATIONAL ASSOCIATION OF CEMENT USERS. Philadelphia, Pens \. IRON ORE CEMENT.* By Arthur E. Williams, f Iron ore cement is a product intended to be used in sea water work. This material is now manufactured in Europe under the name of Erz cement. According to Mr. William Michaelis, Jr., J • the process of manufacture is similar to that of Portland cement except that limestone and iron ore are used in place of limestone and clay. United States Consul Thackara§ gives a description of its manufacture as follows: Chalk, flintstone, and finely ground ferric oxide are used. The flint and iron are ground together, then mixed with the chalk and water and screened through a fine sieve. The screened product is clinkered in a rotary kiln and then ground. An average composition of iron ore cement, given by Michaelis is: CaO 63 . 5 per cent A1 2 3 1 . 5 per cent Si0 2 20.5 " MgO 1.5 " Fe 2 3 11.0 " Alkali 1.0 The effect of sea water is undoubtedly two-fold. In the first place chemical reaction may take place between certain con- stituents of the cement and the salts in sea water, and, on the other hand, the mechanical action of the waves carrying large amounts of sand, freezing, thawing, and the varying pressure of the water due to tide help to injure the cement submerged in sea water. This work, however, will be confined to the chemical action of sea water, for the mechanical action is of minor import- ance unless the cement is weakened by chemical changes. The reactions which take place between Portland cement and sea water are said to be of three distinct kinds. First, the action of MgCl 2 and MgS0 4 in sea water on the calcium hydrate formed during the hardening process of the cement, forming Mg(OH) 2 , CaCl 2 , and CaS0 4 . Second, the action of gypsum, * Under the direction of Mr. R. T. Stull. t Urbana, 111. A Thesis for the Bachelor of Science Degree in Ceramics, University of Illinois in 1910. X Eng. News, Vol. 58, pp. 645-646. { United States Consular Reports. June, 190S. U) 2 Williams on Iron Ore Cement. CaS04 formed above, upon the calcium aluminates forming calcium sulpho aluminate. Third, the crystallization of the gypsum and calcium sulpho aluminate giving an increase in volume, thus causing the disintegration of the mortar. That free lime is present in set Portland cements is well known. Lamine* found 32 per cent of CaO in cement sub- merged in the Black Sea 15 years. Every analysis of a cement exposed to sea water shows a high percentage of MgO. Vicatf in 1840 showed this fact clearly, a cement, which was submerged in sea water for 6 months, was analyzed. A sample, taken from the surface exposed to the sea, showed 10.4 per cent MgO and 19.3 per cent CaO while the interior, which was not impaired, showed 1.87 per cent MgO and 31.33 per cent CaO. A. Meyer J states that cement loses strength in sea water. The MgS0 4 acting with the silicate of lime forms Mg(OH) 2 and calcium sulphate. The CaS0 4 reacts with the calcium aluminates (A1 2 3 , x CaO) of the cement, forming Al(OH) 3 + 3 Mg(OH), + CaS0 4 + CaCl 2 . Charles J. Potter§ says that MgS0 4 is the most active con- stituent in sea water on cement. He found that MgCl 2 softens cement but causes no expansion. Potter says that it is now definitely believed that magnesium salts act on the feebly com- bined lime and alumina compounds which on taking up water of crystallization cause bursting of the concrete. He mixed calcined red brick clay with Portland cement clinker in propor- tions of 6 to 10. From this mixture briquettes were made and placed, together with Portland cement briquettes, in fresh water, sea water, and sea water to which 10 per cent MgS0 4 was added. Both of these cements gained strength in fresh water. In salt water, the Portland cement briquettes began to fail after 5 weeks and were disintegrated after 5 years. These cements showed blistering after one year, which was followed by expansion and bursting. The red cement improved continually but took 8 weeks to obtain the maximum strength that the Portland cement had obtained in 5 weeks. In the 10 per cent solution of MgS0 4 , the Portland cement tested 500 lb. in a month and then went * he Ciment, 1901, pp. 111-691-81. t Iron Ore Cement — The P. C. Co. of Hemmoor, Hamburg, Germany. } Chemisettes Central BUM, Vol. 73. p. 1368. §Jour. Soc. Chem. Ind., Vol. 28. Williams on Iron Ore Cement. 3 back to zero in 1 year. The red cement began at 250 lb. and increased continually to 1015 lb. in 8 years. Mr. Potter says that the chemical combination of CaO, Si() 2 , and AU0 3 and water is feeble and that probably accounts for the ability of magnesium in sea water to be so active. The experiments of Dr. Michaelis* and Le Chatelierf lead them to the conclusion that Portland cement suffers in solutions containing sulphuric acid salts, which applies to sea water. A double salt is formed composed of gypsum and calcium aluminate. This sulpho-aluminate, A1 2 3 , CaO -+- 3CaS0 4 , is said to crystal- lize with 30 molecules of water, which process must be accom- panied by considerable expansion. Le Chatelier says that "the main cause if not the sole cause, of the injuries which cements suffer under the action of sea water is the formation of calcium sulpho-aluminate. Rebuff at + says on the contrary that sulpho-aluminates cannot exist in cements in sea water but agrees with Michaelis and Le Chatelier that calcium aluminates are the parts of cement most easily acted upon by salts in sea water. It has been shown that calcium ferrates are formed similarly to the calcium aluminates and that alumina could be replace* 1 by ferric oxide in Portland cement. Dr. Michaelis puts this knowledge into use with the idea of overcoming the disintegra- tion in sea water. The result of this application is the Iron Ore cement of today. Dr. Michaelis and the Royal Experiment Station of Charlot- tenburg have tested these cements in comparison with Portland cements in a very thorough manner. Mr. William Michaelis§ says in a paper read in the United States that tests of Erz cement and Portland cement were made with both neat and 3 to 1 mix- tures which were placed in fresh water, sea water, and water containing five times more salt that sea water. In sea water, the Krz cement developed a much greater strength than the Portland. In the strong salt water, the strength of the Portland cement decreased rapidly while the Erz cement showed a steady gain. Briquettes were made of Iron Ore and Portland cement * Ton Industrie, 1S96. p. 838. tic Ciment, 1901, p. 31-32. t Ton Induatrii Zeitung, 1901, p. 272. § Enu. News, Vol. 58, pp. 645-646. 4 Williams on Iron Ore Cement. which were placed in a salt solution of five times the normal strength of sea water under pressure of 15 atmospheres for a few days. This condition destroyed the Portland cement bri- quettes entirely, while the Iron Ore cement increased in strength. The Royal Experiment Station conducted similar tests to the above but much more elaborate. Two Iron Ore and three Portland cements were made into prisms, using a 3 to 1 mixture of standard sand and cement. These prisms were placed in sea water and water containing five times the percentage of salts in ordinary sea water. In addition to this, these three solutions were allowed to act upon test pieces made of cement mixed with varied amounts of gypsum. All the Portland cement mortars disintegrated in the three- and five-fold salt solutions; all the Iron Ore cement mortars remained intact and sound. United States Consul A. W. Thackara* investigated this cement for use on the Panama Canal. The result of his investi- gations was the adoption of this cement for concrete work exposed to sea water. Another point in favor of this cement is the property of slower setting. The cement is weaker than Portland for the first week, but then gradually gains strength and exceeds that of Portland. Publications of previous experiments do not show definitely the best composition for cements giving the greatest protection against sea water. With this idea in view, the following investi- gations were undertaken: The outline of procedure in these experiments is as follows: Newberry's cement formula, x (3CaO, Si0 2 ) + y(2CaO, A1 2 3 ), was used as a basis. Assuming, according to Newberry, that Fe 2 3 could replace A1?0 3 and form 2CaO, Fe 2 3 , a triaxial dia- gram was plotted (Fig. 1), the three members stationed at the three corners being 3CaO, Si0 2 , 2CaO, A1 2 3 and 2CaO, Fe 2 3 . By blending these three members, cements could be obtained containing various amounts of the calcium aluminate and the calcium ferrate. The batch weights of these three members were calculated and about 15 kg. of each were weighed up, using practically chemically pure materials. Whiting, flint, aluminium hydrate, and red oxide of iron were the only ingredients. These batches * United States Consular and Trade Reports, June, 190S. Williams on Iron Ore Cement. 5 were ground in a ball mill, then passed through a 200-mesh sieve; thus getting thorough mixing and a finely ground batch. The formulae for the cements made are given in Table I. The following cements, No. 19, 20, 21, 22, 23, 24, 25, 36, 37, 38, 39, 40, 42, 48, 49, 50, 51, 52, 53, 54, 58, 59, 60, 61, 62, and 65 on triaxial diagram were then weighed up, blunged thor- oughly, and partially dried by pouring the slip into plaster molds. ^CaOj^AAOiJ o e> o ' / r\ / <* /io ih v° 3*0 -fc /d / z\ jr K° G °/ /7 2&J 3Z AiO •Sb/ff 27 / sh 44 V 46\efl *h& \ 26 iy 43 A/ ^AfiO Jh/t /a/ ZS / 42 41 \/ SSj/ 5Ai0 V \ V * /\ */\ */\ ' • * ' \ 7\ 7\ /\ >// 2t/ 22./ Ja. 30 J?i OS. GtJ 6S/ 6G\ FIG. 1. TRIAXIAL DIAGRAM. The cements were then rolled into small balls about the size of a marble, dried, dehydrated in a down draft kiln to about 800° C. and placed in fruit jars ready for burning. These cements were burnt in a magnesite test kiln, designed by Mr. Stull of the Ceramic Department, especially for burning experimental cements. The construction of this kiln is shown in Fig. 2. The success of this kiln is a noteworthy fact as test 6 Williams on Iron Ore Cement. kilns suitable for this purpose, heretofore, have not been very satisfactory owing to lack of control, unevenness of temperature in the clinkering chamber. Kerosene oil was used for fuel with an air pressure of about 50 lb. The temperature at the time the clinker was drawn from the kiln was determined first by means of a Wanner pyrometer. This was given up, however, as the rapid rate of burning required a higher temperature than the true temperature of clinker forma- tion. Table I. — Formulae of Cements Made. No. Formulae. Molecular Ratio Si0 2 :A10+Fe 2 0a 19 l(3Ca0,Si0 2 ) 4-.2(2CaO,Al 2 3 ) 4-.7(2CaO,Fe 2 3 ) 0.11 20 .l(3Ca0,Si0 2 ) 4- 1 (2CaO,AkOs) 4-.8(2Ca0,Fe 2 3 ) 0.11 21 l(3CaO Si0 2 ) 4- 9(2Ca0,Fe>0 3 ) 0.11 22 2(3CaO,Si0 2 ) + .S(2Ca0,Fe 2 3 ) 0.25 23 .2(3CaO,Si0 2 )4-.l(2CaO,Al 2 3 )4-.7(2CaO,Fe 2 03) 0.25 24 .2(3CaO,SiO»)4-.2(2CaO,Al 2 3 )4-.fi(2CaO,Fe 2 3 ) 0.25 25 2(3CaO,Si0 2 ) 4-.3(2CaO,AW> 3 ) +.5(2CaO,Fe 2 Os) 0.25 36 3(3CaO,Si0 2 ) 4-.2(2CaO,Al 2 3 ) 4-.5(2CaO,Fe 2 C 3 ) 0.43 37 .3(3CaO,SiOo) 4-.l(2CaO,Al-0 3 ) +.6(2Ca0,Fe»0 3 ) 0.43 38 ,3(3CaO,SiOs) + .7(2CaO,Fe 2 3 ) 0.43 39 .4(3CaO,SiOj) 4-.6(2CaO,Fe 2 3 ) 0.66 40 .4(3CaO,Si0 2 ) 4-.l(2CaO,Al 2 3 ) 4-.5(2Ca0.Fe 2 3 ) 0.66 42 .4(3Ca0.Si0 2 ) + .3(2CaO,Al 2 3 ) +.3(2Ca0,Fe'>0 3 ) 0.66 48 5(3Ca0.Si0 2 ) 4- 3(2Ca0,Als0a) 4-.2(2CaO,Fe'>0 3 ) . . . 1.00 49 .5(3Ca0,Si0 2 ) +.2(2CaO,Al>0 3 ) +.3(2CaO,Fe 2 3 ) 1.00 50 .5(3CaO,Si0 2 )4-.l(2CaO,AM) 3 ) +.4(2CaO,Fe-0 3 ) 1.00 51 .5(3Ca0,Si0 2 ) +.5(2CaO,Fes03) 1.00 52 .6(3CaO,Si0 2 ) 4-.4(2CaO,Fe»0 3 ) ... 1.50 53 .6(3CaO,SiO-) +.l(2CaO,A1.0 3 ) 4-.3(2CaO,Fe 2 Os) 1.50 54 .6(3CaO,Si0 2 ) +.2(2CaO,AM) 3 ) +.2i2CaO,Fe 2 3 ) . . . 1.50 58 .7(5CaO,Si0 2 ) 4-.2(2Ca0,AI-0 3 ) +.K2CaO,Fe 2 3 ) 2.33 59 .7(3CaO,Si0 2 ) 4-.l(2CaO,Al 2 Os) 4-.2(2Ca0,Fe 2 3 ) 2.33 60 .7(3CaO,SiOs) 4- 3(2CaO.Fc-.0 3 ) . . . 2.33 61 8(3CaO,Si0 2 ) 4- 2(2CaO,Fe-0 3 ) 4.00 62 .8(3CaO,Si0 2 ) +.l(2CaO,Al->0 3 ) 4-.l(2CaO,Fe 2 3 ) 4.00 65 .9(3CaO,Si0 2 ) 4-.l(2Ca0,Fe 2 O 3 ) 9.00 Almost all of these cements were fused till the surface was glassy in appearance before the cement seemed well clinkered and crystals appeared. Cements No. 54, 58, 62, and 65 appeared like a Portland clinker, except darker in color and were not fused or slag-like in appearance. The clinker was first reduced in a jaw crusher and then ground in a disc mill; a screen test showed 24.2 per cent on 150 mesh screen; 12.3 per cent on 200 mesh screen; and the remainder, 63.5 per cent passed 200 mesh. These cements show that they are approximately of the same degree of fineness as the average Portlands. After the samples were ground, pats were made from Williams ox Iron Ore Cement. si y ii r~T~i : i -*- L fl > « 1 \ f x r FT-n ! ' '*— i ®!t 5 5 'l I s Williams on Iron Ore Cement. them in the usual manner to determine the properties of the cement. The amount of water used for mortar was determined by the Boulonge method (Waterbury's Cement Manual, p. 44). The initial and final sets were determined with Gilmore needles. Four pats were made of each cement with the idea of using one for the time of setting tests and placing the other three imme- diately in the moist closet, two of which were to be used for the boiling test after 24 hours, the third to be allowed to stand in Table II. — Results of Tests on Cements. Time of Time of Water Remarks Conditions No. Initial Set, Final Set, Used, at Time of after 4S Hours hours. hours. per cent. Final Set. in Moist Closet. 19 IX 3 21.0 Cracked in X hour Cracked 20 1 5 20.0 O. K. Strong Warped and cracked 21 2X 5X 21.0 No cracks No cracks 22 IH 4 20.0 Small cracks No cracks 23 i 21.0 Cracked No cracks 24 % "hX 22.0 Cracked No cracks 25 IX 21.5 Cracked No cracks. Soft 36 i% ii 20.0 Cracked O. K. 37 i 2X 20.0 Cracked No cracks 38 i 5 20.0 0. K. No cracks 39 2 8 21.0 Cracked Cracked 40 IX 3X 20.0 Cracked Warped 42 X 2% 21.5 O. K. No cracks 48 1M 7 22.0 O. K. No cracks 49 IX 3 21.0 Cracked Cracked 50 3 22.0 Cracked No cracks. Soft 51 2 io 21.0 O. K. Soft 52 1 9 20.0 Soft Soft 53 \x 4 21.0 Cracked No cracks. O. K. 54 1 iX 23.5 Cracked No cracks. O. K. 58 1 3X 22.0 No cracks Cracked 59 X 4X 21.0 O. K. Warped 60 IX 5 21.0 Soft and crumbly Warped and cracked 61 1 6 22.0 Warped O. K. 62 IX 22.0 Did not harden O. K. 65 IX 21.0 Cracked Warped water for 28 days. All of these cements went to pieces in cold water or in the boiling test. The results are given in Table II. From these cements, one only, i. e., No. 62, remained sound when placed in water. This cement also stood the boiling test (| hr.), the others going to pieces. The molecular ratio of Si02 to AI2O3 for this cement is four and since the molecular ratio for good cements is between 5.1 and 6.8 and since none of these cements lie between these limits, it was decided to construct a new group. Cement No. 62 approached these ratios nearer than any other. Williams on Iron Ore Cement. 9 A new hatch was calculated after Bleininger's formula (2.8CaO,Si0 2 ) + (2CaO, A1,0 3 ) having different amounts of Fe 2 3 and AhO : , and also the ratio of SiO a to AhO ;i -+■ Fe 2 3 varied from just above to just below the limits. The using of chemically pure raw materials in place of slag and limestone gives less efficient mixtures of lime and Si0 2 . It was, therefore, thought that sufficient lime would he obtained by the use of Bleininger's formula. For formula 1 see Table III. Table III. — Formcl.e fob Cements Made. No. Formulae. -4i At A 3 A, B, B 2 B 3 B 4 Ci Ci C 3 d 5.1(2.8CaO,Si0 2 )+(2Ca ,Fe0 3 ) .VN(2,SCa< ».Si<>.) 4-(2CuO.Fi->0 3 ) 6.4(2.8< !a< ),Si( h) 4-(2CaO,FesOs) ".(l(2.sCaO.Si02)+(2Ca(),Fc 2 3 ) 5 2S 2 8CaO.SiOs) +0.175(2CaO,AbOa) +.825(2CaO,Fe20s) (i.0()(2.sCa( >,Si( >») +.l75(2Ca< ),AUOj) +.825(2CaO,Fe20a) 6.40(2.8CaO,SiO2) H-.200(2CaO,AliO8) +.800(2CaO,Fe 2 O3) 7.22(2.8CaO,Si0 2 ) +.175<2CaO,Ab( >s) +.825(2Ca< >,Fe 2 3 ) 5.44(2. SCaO,Si0 2 ) +.360(2CaO,Al,.< >j) +.640(2Ca( ),Fe 2 3 ) 5.80(2.8CaO,S1Os)+.400(2CaO,Al2Os(+.600(2BaO,Fe2O 3 ) 6.40(2.8CaO,SiO 2 ) +.400(2CaO,Al 2 O 3 ) 4-.«00(2CaO,Fe 2 O 3 ) 7.00(2.SCaO,SiO 2 ) +.400(2CaO,Al 2 O 3 ) +.600(2CaO,Fe 2 O 3 ) Percentage Composition. Molecular No. CaO AhOs Fe 2 3 Si0 2 Ratio R 2 3 :Si0 2 -4i 66.0 0.0 11.6 22.4 5.1 At 66.7 0.0 10.4 22.9 5.8 -4 3 67.2 0.0 9.6 23 . 2 ti.4 A, 67.5 0.0 8.9 23.6 7.0 Bi 66.7 1.3 9.4 22.6 5.25 B 2 67.4 1.1 8.4 23.1 6.00 Bz 67.5 1.3 7.8 23.4 6 Hi B, 68.1 0.9 7.2 23.8 7.22 Ci 07.4 2.5 7.2 22.9 5.44 C 2 68 2.7 6.0 23.3 5.80 C 3 68.2 2.5 5.8 23 . 5 6.40 d l,S .", 2.3 5.4 23.8 7.00 These cements were prepared in the same manner except that the temperature of clinkering was determined as near as possible by the method used. The kiln was allowed to cool to about 1000 deg. C. before a hatch of cement was put in and tem- perature was then gradually raised till clinker was formed, the temperature was then read with a Wanner pyrometer. The clinkers obtained appeared exceptionally good, being dull black in color and glistening brightly in the sun. These 10 Williams on Iron Ore Cement. clinkers were pulverized the same as has been previously de- scribed, then tested. The results of these tests, Table IV, show that good cements can be obtained with a large amount of alumina using the same ratio of Si0 2 to R 2 3 as Portland cements require. One very noticeable fact, however, is that when no A1 2 3 is present as in series A, A- 2 , A 3 , and A4 these cements all show expansion, thus giving evidence of free lime. Although A\ stood the boiling test, the cubes made from this cement bulged out from the mold considerably. The question arises at this point, is it always necessary for AI0O3 to be present or can a good cement be made without it? Table IV. — Results of Test. Temperature Time to Clinker, hours. when Appearance Initial Set, Final Set, H2O, No. Clinkered, deg. C. of Clinker. hours. hours. per cent. A\ 1300 X 24 62 24.8 Ai 1320 V2 All 22 56 24.0 -4 3 1320 l l A clinkered 26 56 23.2 Ai 1330 V2 good, 2S 60 26.0 Bi 1390 V2 colored black 4% 40 26.3 £2 1320 IX and 4^ 44 24.4 B 3 1350 X glistening 11 36 28.0 Bt 1400 IV* with 5 4S 25.0 Ci 1320 Wi crystals 5 30 24.4 Ct 1320 X in a 12 40 24.0 C 3 1330 ix bright 12 48 28.0 d 1380 y 2 light 17 40 27.2 This ought to be possible by reducing the lime content, as Ai was the best of series A and also had the smallest amount of lime silicate. The slowness of setting is another factor which must be considered. It will be seen by Table IV that all of the cements required a long time to harden. This must be carried on in a moist atmosphere also or the cement will dry out before it has completely hydrated and set. The above factors will perhaps limit the use of this cement to work under water which may be allowed to set a considerable time. All the cements of series B stood a 6-hr. boiling test with- out showing any signs of expansion. In series C all but G stood the boiling test. & warped a little and came loose from the glass Williams on Iron Ore Cement. 11 plate although the cement has a comparatively low lime content and its formula lies between other good cements. The attempt was next made to give these cements a com- parative test with Portland cement to show their relative resist- ance to sea water. The method used was similar to that of Dr. Michaelis. One-inch cubes were made of each series of cements together FIG. 3. — STEAM CYLINDER. with a set of cubes of a standard commercial Portland cement, which had stood all the commercial tests. These were allowed to stand 60 hr. in the moist chamber and then placed in water, remaining in water for 27 days. The cubes made from series A together with a set of 5 Portland cement cubes were placed in a steam cylinder, Fig. 3, containing an artificial sea water solution of ten times normal strength. The quantity of salt is shown in Table V. The cements were then put under steam pressure 12 Williams ox Iron Ore Cement. of 125 lb. or 8| atmospheres, the temperature being between 150 and 200 (leg. C. This was continued for 3 days. On opening the cylinder, the salt solution was found to be very dilute due to condensation of steam and no visible action on the cements had occurred. The salt solution and cubes were then put into a large wide-mouthed bottle, provided with a stopper and small vent hole. The bottle was then placed inside the pressure cylinder and steam admitted, allowing little or no condensation. After being sure that the bottle was not broken by the first change in temperature, the pressure was kept on for 3 days longer. Upon opening the cylinder, the cubes were found bone dry and covered with salt and the bottle cracked. This was due, no doubt, to the rapid reduction of the pressure, allowing the water Table V. — Analysis of Sea Water.* 37.3 parts per thousand parts water. 100 parts =2700 parts water. 12000 2700 Salt. Per cent of Salt. Ten tin ?es per cent of Salt. Total for 12 liters of Water. NaCI MgCb MgS0 4 CaSOi K^SOj 77.75 10.87 4.73 3.60 2.46 10S.7 47.3 36.0 342.10 478.28 208.12 158.40 10.80 MgBr CaHC03 0.217 . 34.5 0.93 1.62 = 4.4 factor times per cent of salt =quantity per 12 liters of water. to vaporize rapidly, which was at a temperature above its boiling point. The results of this test were contrary to what was expected as the Portland cements were untouched and all of the iron cements were cracked and swollen. This cracking and swelling is caused, no doubt, by an excess of free lime, as these cements showed an expansion in the boiling test and there was a deposit of hydrated lime in the bottom of the cylinder which seemed to have been leached out of the cubes. No crushing strength test of Series A was made as they were all destroyed already. Series B was then placed in the cylinder, with a set of Port- * University Geological Survey of Kansas, Vol. 7, p. 27. Williams on Iron Ore Cement. 13 land cement cubes. A vessel made of 4-in. pipe was used in place of the glass bottle to overcome cracking due to sudden change in temperature. This series was kepi under pressure for 6 days, and when removed from the cylinder neither the Portland or Iron Ore cements appeared harmed except cement B 3 which went to pieces. The reason for the disintegration of this cement is unexplainable except that it was not clinkered properly. The boiling test, however, showed a good cement. (Table VI.) As the crushing strength tests of the Portlands show, there seemed to be no weakening due to being in the salt solution. Table VI. — Results of Boiling Test for 6 Hours, after 60 Hours in Moist Chamber. Number. Appearance after Sea Water Test. Ai Good, cracked plate. Came loose from plate and showed some expansion. Same asA3. Good. Came loose from plate, warped. Good. Good. At... A, | I Bi Bi £ 3 b\ ::::.. Ci Ci C 3 C t Also the strength of the Portlands seems to average higher than the Iron Ore cements. (Table VII.) Five cubes of each cement of Series C were then placed into the cylinder with a set of Portland cubes made at the same time. These were kept under pressure for 8 days. The results of this series were quite different as 4 of the 5 cement cubes were badly cracked and had begun to swell. C 2 , C 3 , and C 4 showed no signs of disintegration, but C\ was cracked and swollen badly. This cement, as the A Series, did not stand the boiling test and such an action would be expected from it under the extreme condi- tions in the pressure cylinder. The crushing strengths of C 2 , C3, and C 4 averaged lower than the B Series, C 2 was so soft that disintegration had evidently set in. 14 Williams on Iron Ore Cement. Table VII. — Crushing Strength of Cements. Pi B 2 C 2 Cz C t No. Cross-sectional Area, sq. in. Crushing Strength. Average, lb. per sq. in. Total lb. Lb. per sq. in. Pi Pi = Portlands in fresh water 3 weeks. 1.08 7680 7100 0.975 4780 4900 1.06 6650 6280 1.045 5650 1910 1 . 105 7750 7020 6042 p 2 = Portland cement in fresh water 4 weeks. 0.97 7850 8700 0.95 6620 6970 0.97 7730 7960 P= pressure with Series B of the Iron Ore Cements. 7876 0.97 1.25 1.025 0.98 1.01 5420 4860 7650 7330 7200 3890* 7470 7470 7150 6920 Iron Ore Cement in salt solution under pressure cylinder 6 days. 5620 6250 4915 4460 4860 6500 6000 7100 7550 5930 4120 4820 4540 6240 5350 4080 4360 6660 5310 4660 2190 1660 2400 1SSO 24 SO 3000 6150* 3331 1 4SO0 3900 Portlands in Cylinder 7 days with Series C. 1.035 5810 1 . 075 6720 1.035 5120 1.06 4740 1.045 5200 1.105 7170 1.02 6620 1.055 7500 1.115 8430 1.125 6680 1.09 4480 1.075 5180 1.10 5000 1.06 6610 1.12 6000 1 . 025 4200 1.03 5400 1.025 6320 1.1 5850 1 04 4850 1.05 2280 0.97 1580 1.1 2640 1.00 1820 1.01 2500 1.07 5220 1.07 6630 1 . 06 3630 1.07 r,l to 1.04 4 ().-)() 5241 6616 5014 4914 2110 5757 0.99 0.97 3000 6720 3030 6930* Only unaffected Portland cement cube. * Signifies not calculated in average. Williams on Iron Ore Cement. 15 Conclusions. As the time for this investigation was limited, further work could not be done, and the conclusions which may be drawn from these results are limited. This much may be said, however: 1. The amount of lime or silicate of lime ought to be less when Fe 2 03 alone is used in place of AI2O3, as the lowest ratio of Series A 5.1 was the only one which stood the boiling test. Scries B showed that the limits gave good cements throughout, neglecting B 3 which must have disintegrated due to some other cause. Series (' showed that the lime and silica required increased as the lower ratio 5.44 disintegrated and the higher ratios were good. To sum this up, when all iron is used the R 2 3 : Si0 2 ratio should be below 5.1; when 0.175 to 0.2 mols. A1 2 3 is used with 0.825 to 0.8 mols. of Fe 2 3 the ratios lie between 5.1 to 7.22. If 0.36 to 0.4 mols. of A1,0 3 the ratio must be 5.8 or greater. This is but a suggestion and will require further experimenting to show it definitely. 2. That cements with large amounts of Fe 2 3 will stand saline solutions better than cements containing A1 2 3 was shown in the test of Series C where the Portlands were actually disinte- grated and the iron cements stood the same test. 3. The results seem to suggest that if the amount of lime was reduced lower than 2.8 CaO in Bleininger's formula, better strength could be obtained. There was found in the bottom of the vessel, after each trial in the cylinder, a heavy muddy deposit which was principally hydrated lime and which appeared to have been Leached from the cubes. This reduction of the amount of lime may not need to be as much as the results suggest if the raw materials were clay and limestone in place of pure whiting, AloCOH),; and flint. All of the iron cements would have stood the tests better if they had been allowed to stand in the atmosphere and age, thus giving the lime time to become calcium carbonate. The Portland cement, which these cements were tested against, was one of the best cements on the market. It tested as follows: Initial set, 3 hr.; final set 4 5 hr. ; tensile strength of neat cement after seven days, (57!) lb.: after 28 days, 774 lb.; and its crushing strength is shown in the tables. This cement had also aged several months in the Laboratory and was in the best of condition 16 Williams on Iron Ore Cement. to stand accelerated tests. The percent of lime given by Mr. William Michaelis is 63.5 per cent with a small amount of magnesia, MgO, 1.5 per cent. The cements made for this thesis are all above 66 per cent, this is only another evidence that these con- clusions are correct and the following formula is suggested as the center of a series of cements for further experimenting: 4(2.8 CaO,Si0 2 ) 0.8 (2 CaO, Fe 2 3 ) 0.2 (2 CaO, A1 2 3 ). from this vary both the amount of Si0 2 and CaO. Bibliography. William Michaelis, Jr., Engineering News, Vol. 58, pp. 645-646. Charles J. Potter, Journal Society Chemical Industry, Vol. 28. Newberry, Journal Society Chemical Industry, Vol. 16, No. 11. A. Meyer, Chemisches Central Blatt, Vol. 73, p. 1369. A. Spencer and E. C. Eckel, Patent No. 912,266, U. S. Karl Zulkowski, Chemische Industrie, 1901. A. W. Thackara, U. S. Consular Reports, June, 1908. Iron Ore Cement, The P. C. Co. of Hemmoor, Hamburg, Germany. Lamine, Le Ciment, 1901, pp. Ill, 691, 81. Dr. Michaelis, Tone Industrie Zeitung, 1896, p. 838. Rebuffat, Tone Industrie Zeitung, 1901, p. 272. Le Chatelier, Le Ciment, 1901, pp. 31-32. £n JUN 3 ° 1915 UNIVERSITY OF ILLINOIS BULLETIN ISSUED WEEKLY Vol. XL JUNE 29, 1914. No. 44 [Filtered as second-class matter December 11, 1912, at the post office at Urbana, Illinois, under the Act of August 24, 1912.] BULLETIN No. 20 DEPARTMENT OE CERAMICS R. T. STULL, Acting Director DESIGNS OF SEVEN TEST KILNS BY R. T. STULL andR. K. HURSH PUBLISHED BY THE UNIVERSITY OF ILLINOIS, URBANA 19 13-1914 DESIGNS OF SEVEN TEST KILNS BY K. T. STILL AND K. K. UIKSII, 1KUAXA, ILLINOIS Iii presenting the designs of these test kirns, no claims are made to original ideas. In the design of each kiln, an attempt has been made to combine well-known principles in such a man- ner as to best meet the conditions and requirements which the kiln is to meet. All flues leading from the kilns are placed under the floor. These connect with two main tines 15 in. wide by 30 in. deep, which in turn connect with a 60 ft. stack. Kiln represented by Figs. 1 and 2 is of the down-draft, open fire type, provided with two fire boxes. The fire boxes are short and wide, facilitating easy cleaning and prolonged life of grate bars. The kiln is provided with a flue system so that forced draft may be applied either above or below the grates. The kiln has been in use over two years and has been fired repeatedly to cone 16. It has a surplus of draft so that it has not been necessary to use forced draft to reach high temperatures. In Figs. 3 and 4 is shown a recta nglar down-draft muffle kiln. The muffle is 2 ft. by 3 ft. and 3 ft. to the spring. The muffle walls are laid with hollow blocks beveled at the corners in order to give greater radiation surface. The same size and style of fire box is used in this kiln as in the former one. The kiln has been burned to cone 8 in twelve hours. After two years of use. it is in excellent condition. Figures 5 and (i represent a round down-draft open fire kiln. Fuel oil, delivered to the kiln under 5 lb®, pressure, and air at 2 lbs. are used in firing. The four burners lead tangen- tially into a combustion ring. The fire gases pass up over a cir- cular Hash wall and down through the perforated floor. The crown is removable and is raised and lowered by a three ton chain hoist running on a track. This arrangement permits of easy and quick setting and eliminates the troublesome cold doorway. The temperature and kiln atmosphere can be gov- erned very closely. The kiln has been in use for more than a DKSKiXS OF SEVEN TEST KILNS DESIGNS OF SEVEN TEST KILNS 5 year. Although it is capable of attaining very high tempera- tures, there has beeD no occasion to fire it above cone 8. This temperature has been attained with only two burners in use. Figures 7 and 8: Open fire, dowu-drafl kiln: The kiln is fired by gas and compressed air, both being preheated in coils of wrought iron pipe suspended in the out-going flue. The flue is provided with an opening just below the damper. Through this, air can be admitted in order to prevent over-heating of the coils. The kiln is hi-ed by ten burners made from ordinary pipe fittings. Each burner is about the size of an ordinary Bunsen blast lamp. The kiln has been fired to eone 14 in six hours. DKSKiXS OF SEVEN TEST KILNS DESIGNS OF SEVEN TEST KILNS The setting chamber i.> 12 in. by 22 in. by 9 in. to the spring, and -4 in. rive. The kiln is especially adapted to clay testjng. Two pings in tin- crown, ape in the hack and one in the wicket, are provided for drawing trials, Fig. i Figure 9: Battery of three calcining kilns: Kadi unit is fired by fuel oil and compressed air. The combustion chamber at the top is cylindrical in form, the Same entering tangentially. Each unit is provided with two calcining chambers. The kilns are designed especially for burning small batches of Portland cement, and for calcining clays and dry colors. The material 8 DESIGNS OF SEVEN TEST KILNS to be calcined may be placed on the bottom plate of the chamber or in covered flat tile saggers. Figure 10 : Twin muffle kiln : The kiln was designed es- pecially for firing enamels for metals and overglaze colore. Each muffle is heated by two gas burners, the air being preheated in the recuperator below the muffle. The gas passes in horizontally and meets the air coming up from the recuperator. The flame passes back to the opposite end of the muffle then turns and passes twice around the muffle to the center and down into the recuperator. The hottest parts of the flames from the two burn- ers applied to each muffle, moving in opposite directions, encircle the muffle ends first, then encircle the middle, thereby neutraliz- ing the "cold end" effect and giving a more uniform muffle temperature. Figure 11 : Battery of four drop-frit furnaces : Each fur- nace is fired by two small gas burners made from pipe fittings. The gas and air are preheated in wrought iron pipe coils placed in the outgoing flue. The flames pass into the combustion ring tangentially, then pass over a flash ring and down around the crucible. The frit pan underneath when filled with water forms a "water seal." The bottom of the pan is curved so that the frit can be raked out, making it unnecessary to remove the pan. The principal objection in the construction of the furnace is that the frit pan is too close to the fire. It should be placed about two to three courses of brick lower in order to obviate the rapid evaporation of the water and the burning of the top of the pan. Ceramic Laboratories. University of Illinois DISCUSSION Mr. Blair: Will Professor Stull give us an idea of the cost of bui'iiin g. that first kiln? Prof., Stull: Yes. I can give you an idea of the cost. Like Professor Bleininger, I did not want to scare you to death with the figures. A large fill was made on the present site of the new kiln house. In building the foundations for these kilns, it was necessary to go down so deep to get solid ground that it brought DESIGNS OF SEVEN TEST KILNS 9 up t lie casts enormously. The cost of that, pari below ground is nearly as much as that above ground. The first furnace shown cost between seven hundred and eight hundred dollars, that is, as near as I can remember. The figure given is for the kiln complete, including foundation, dues, iron work and all. Plenty of iron work has been placed on all kilns with a view to having them well braced. 1.0 DESIGNS OF SEVEN TEST KILNS Q Z uJ -1 s 2 1 li- f- _J -O — UJ O P DESIGNS OF SEVEN TEST KILNS 11 Fig. 6 12 I) SKiXS OF SKVKX TEST KILNS '^HHHhHHH DESIGNS <»F SEVEN TEST KILNS 13 14 designs ok Seven tkst kilns <& ' ■ * ■- - f*fi ^L - . y k .... ^ . sl_ DESIGN'S OF SEVEN TF.KT KII.NM 15 ^^MBESSaMm HHHHHHHHHHMHhHHhHH L*4 t* : 16 DESIGNS OF SEVEN TEST KILNS UNIVERSITY OF ILLINOIS BULLETIN I S S V E I) W E E K L Y Vol. XI. JULY 6, 1914. No. 45 [Kntered as second-class matter December 11, 1912, at the post office at Urbana, Illinois, under the Act of August 24, 1912.] BULLETIN No. 21 DEPARTMENT OF CERAMICS R. T. STULL, Acting Director DEFORMATION TEMPERATURES OF SOME PORCELAIN GLAZES BY R. T. STULL and W. L. HOWAT A TYPE OF CRYSTALLINE GLAZE AT CONE 3 BY C. C. RAND and H. G. SCHURECHT PUBLISHED BY THE UNIVERSITY OF ILLINOIS, URBANA 19 13-1914 W THE Authorized Reprint from Volume XVI, 1914, fransactious \ tear Ceramii 3 DEFORMATION TEMPERATURES OF SOME PORCELAIN GLAZES K. T. STILL A.ND \V. L. HOWAT, I'KBAXA, ILL. The group of glazes studied comprises ten horizontal series designated by letters from A to J, each series consisting of ten members. The group of one hundred members covers the fol- lowing limits represented by the four corner glazes : TABLE I — FORMULA OF CORNER GLAZES GLAZE K.O CaO \! ii SiO. \-l 0.3 0.?. 0.3 0.3 0.7 0.7 0.7 0.7 0.40 . 40 0.85 0.85 2.0 A-10 6.5 T-l 2.0 T-io 6.5 TABLE II — BATCH WEIGHTS BRANDY- WINE FBIiDBPAB WHITING Rate. No. 20 BALL CLAY N. C. KAOLIN FLINT AUOH), A-l 167.4 167.4 167.4 167.4 70.0 70.0 70.0 70.0 12.!) 1 2 . 9 12.9 70.9 12.9 12.9 12.9 70.9 270.0 216.0 A-10 T-l 70.2 T-10 Different members in the group were made by molecular blending of the four extremes. These were applied to bisque wall tile, set in saggers in a down draft kiln and burned to cone !> in 40 hours. ('ones were also made from the glazes and their deforma- tion temperatures determined in a platinum resistance furnace, the temperatures being measured by a platinum, platinum-rhod- ium thermocouple and a Leeds-Northrup direct reading poten- tiometer, (accurate to 3 G). 4 DEFORMATION TEMPERATURES OF GLAZES The time-temperature curve followed in all determinations is shown in Figure 1. The temperature was raised to 1200°C. in 120 minutes. Beyond this the temperature rise was 2^ de- grees per minute. A number of deformation tests made on du- plicate Seger cones gave the following results: cone 4 — 1212°C, cone 6— 1255°C, cone 8-1290°C. Deformation-temperature readings were made on two or more cones of each glaze. The variation was rarely over 5 C. and in the majority of tests, duplicate cones gave the same tem- perature readings. TABLE III — DEFORMATION TEMPERATURES COVERING THE LIMITS ''■: ; !> ( ,' ' 0.40 to 0.85 AUO:, : 2.0 to 6.5 SiO, O.i Cat) i ALO, I i I ! I I I I i 1 I -__ J 1277 1246 L232 r235 1 247il252|1248!l260J1267il26o| 0.85 i 1275]1240|I228!1230|1240|1235|1245|1247I1250[1252 0.80 H 1272 1245 12:52 12X0 1 230 '1232 12X51235 1245 1245 0.75 G |l272il240|l228|l228|l232Jl232Jl233|l2::7 1235 1247 0.70 F 126711238 1225 1225 1225 1225J1228|123"5 1235 1245 0.65 E 1232 1225 1225 1222 1220 1225 1228 1235 1245 1245 0.60 D 1230J1225 1225 1227|l230 1230il24o|l245|l248 1252 0.55 C 1232 1228 1228 1228 1228 1230 1240 1248|l252|l255 0.50 B |1235|1230 1228 1233|l235 ! 1245 1254 1252 1257Jl270J 0.45 A 1232 123,2 1240 1245 1245 1255 1255 1268 1272 1277 0.40 M LECULES si0 2.0 2.5| 3.0, 3.5 4.0 4.5 5.0 5.5 6.0| 6.5! The average temperature readings for two or more cones of each glaze of the group are given in Table III. The results of the burn and the iso-deformation lines are represented graphi- cally in Figure 2, the deformation-temperature being indicated in degrees centigrade on each line. The RO is constant for all glazes. The molecular variations of Si()„ are plotted along the abscissa and the molecular varia- tions of ALO, on the ordinate. DEFORMATION TEMPERAT1 KM S OF GLAZES Q Q fc ti ^ ^ 5 & * B) i\ v SL 3&frUMU3ctH/JJ. 6 DEFORMATION TEMPERATURES OF (iLAZES In the lower right corner are the devitrified glazes between the limits : RO, 0.4Al 2 O 3 , 5.0SiO 2 BO, (UAlJL 6.5Si0 2 RO. 0.6Al 2 O 3 , 6.5Si0 2 In the lower portion of the devitrified area the glazes were '■razed. In the center of the field are the brigUrt glazes which were considered matured. Bright glazes which were crazed are found in the lower left corner within the limits: RO, IUALO,, 2.5Si0 2 RO. (UA1,0 3 , 2.0SiO 2 RO, 0.5Al 2 O 3 , 2.0SiO~ At the left of the field a small group of matured mats are found between limits : RO, 0.55Al 2 O 3 , 2.0 SiO, RO, 0.70 A1 2 3 , 2.0 SiO^ RO, 0.65 Al,o : , 2.5Si0 2 In the upper part of the field the glazes were under fired. The difference between max and n:in deformation tempera- tures is 57 ('.. the softest one deforming at 1220°C. having the formula, RO, 0.6 ALO,, 4.0 Si0 2 . The member at the upper left corner (RO, 0.85 ALO,, 2.0 SiO.,) and the one at the lower right corner (RO, 0.4 ALO.,, 6.5 Si0 2 ) deformed at the max tempera- ture 1277 C. Each horizontal scries may be considered as being com- posed of the components, glaze and SiO.,. The broken line CD passes through the deformation-eutectic of each of the ten p'laze — Si0 2 series. In a vertical direction, consider each series made up of glaze and A1 2 3 , the dotted line EF represents the deformation-eutectic axis of the ten glaze — ALO, series. These two axes (CD and EF) cross at the point of lowest deformation temperature (group eutectic). Its deformation temperature is ten degrees higher than the indicated tempera- ture of Seger cone 4. The glazes whose formulae correspond to cones 4, 5 and 6 deformed at 1228 O. 1240^C and 1245°C re- spectively. DEFORMATION TEMPERATURES <>K GLAZES The line AB is the higih gloss axis plotted according to the appearance of the glazed trials. The gloss axis follows roughly parallel to thr glaze-Si< > 2 , deformation-eu, 3.5SiQ 2 Deformation temp. ==1227 C. BO-0.55 A1 2 Q 3 4.0 SiO. Deformation temp. = 1230°C. KO-0.60 ALO,. 3.5 SiO, Deformation temp. = 1222 °C. T&AMS. s4M. C£/?. SOC. l/OL . XW STVLL & HO WAT .20 3 6 4.Z MOLecoies s,o. come eleye/v burn constant { .7 CO SOCWD CtfAZED The difference between the deformation-temperatures of the.se glazes and the temperature to which they were fired (cone 9) is 80' C to 9.0 C, or a difference of 4 to 4U cones. For the purpose of comparison the iso-deformation temperature lines are plotted on the field of porcelain glazes burned at cone 11 and DEFORMATION' TK.M l'KKATl RKS OF ©LAZES 9 jn-o\i( ut>l \- reported, 1 Figure 3. The high gloss axis QT lies to the righl '»i the glaze-SiOj, eutectie axis and crosses the glaze- AL<>. eutectie axis close to the eutectie member of the group. The besl glazes in this group arc found in close proximity to the group eutectie, the same as in the cone !' burn. Not only docs the group eutectie lie near the center of the area of besl glazes, but it is also Located at a safe distance away from devitrification, crazing, matness and immaturity. Ceramic Laboratories, University of Illinois. 1 Influences oi variable silica and Alumina on Porcelain Glazes of Constant RO, Trims. Amrr. Cer. Soc, Vol. xiv, pp. 62-70. A TYPE OF CRYSTALLINE GLAZE AT CONE 3 C. C. RAXD AND II. G. SCHURECHT, 1RBAXA, ILL. The glazes under consideration are of a type designed to mature about cone 3 to 4. The A1 2 3 is maintained constant throughout at .05 equivalent and is introduced as Pikes No. 20 English ball clay. In general the group resembles Worcester's 1 best raw clay glaze. His formula was 0.33% Na 2 | n _ Q | 1.60 Si0 2 O.662/3 ZnO } )m '■> ) 0.20 B 2 3 He concludes, however, that .05 A1,0 3 generally seems the most favorable and that many German formula? call for this amount. A group of 36 glazes was made with a view to determine the effect of varying ZnO against Na 2 along the ordinate, and rutile against Mint along the abscissa. 0SC00) 303 *°3\ fro./ ffl)^f{— .a!' the problem 1ms been to secure .. and shaking. The slips \\\'ix> allowed to stand for a day, after which tlhey were poured into plaster molds. When the excess water had been ab- sorbed the bodies were removed 6rom the molds, and dried in an oven to 200 0. After crushing in a porcelain mortar, triangular floor-tile were made by the dry-press prooess, about LO percent of water being used. They were burned DO cones 5, 7, 9 and 11 in an open, down-draft, gas-fired tesl kiln. Results. Those bodies high in iron were most plastic, and those high iu lime were least plastic. This was shown both by the working properties of the bodies in I he plastic slate and by I lie strength of the dried tile. Vitrification — None id' the bodies were completely vitrified at cone 5, although tho.se high in iron and lime were hard anil dense, those high in lime being the hardest. At cone 7. all bodies containing over four percent of fluxes were vitrified. All bodies were completely vitrified at cone 9, those containing over 7 per- cent of fluxes being overburned. Bodies containing 4 percent and over of fluxes were over- burned at cone 11. The remainder retained their shape but had a glassy surface with the exception of 1, 2 and 3. Color — Bodies Tree I'roni iron burned white and were prac- tically uniform in color at vitrification. Those containing 1 percent of iron were cream colored when burned under oxidizing conditions, but a good uniform gray color was obtained when the tile were reduced at the end of the burn, 'fhe lime had very little effect upon the color of bodies containing 1 percent of iron. Bodies containing '_' percent of iron were pink or light red at cone 5, above which temperature they changed to brownish buff with the exception of No. 4. which became dark yellowish may. Bodies containing 4 to 111 percent of iron burned n'i\ to dark rr(\ at cone."). Those containing I, ."> and ti percent were still red at cone 7. The color was much deeper than at cone 5 and in- 4 CALCIUM \XI> [RON CHLORIDES IX PORCELAIN BODY creased with increased iron. Two percent of lime did not affect the color of bodies containing 5 percent or over of iron. The remainder of the .series did not produce desirable colors for floor tile. CONCLUSIONS Uniform gray colore of pleasing shades can be made by pre- cipitating to - percent of iron in a porcelain body and burning properly. Uniform red colors can be produced by precipitating 4 to 6 percent of iron in a porcelain body which, if burned properly, would not have more than 3 to 4 percent porosity. ( leramic Laboratory, University of [llinois DISCUSSION Mr. Parmelee: 1 should like to ask the reason for using calcium salt. Mr. Eadcliffi : Calcium chloride was added, because it is a. soluble salt; ami it was thought, that the intimate mixture of the calcium and iron obtained in this way, might throw some light on the cause of the varied color effect, produced by iron in different clays. SOME COBALT-URANIUM COLORS r.Y B. s. RADCLIFPB Then- are four coloring oxides, namely, copper, chromium, nickel and iron, which under proper conditions produce green colors in bodies and glazes. In physical mixtures, uc are able to produce greens by blending blue and yellow. The object of this investigation was to determine whether green could be produced by blending cobalt-blue and uranium- yellow. Series A was made up as follows: TABLE I— SERIES A Co*0 3 Na 2 U 2 0, <;H,0 Al,(OH), ZnO 1.0 50.0 40.0 25.0 . 9 50 . 40.0 25.0 0.8 50.0 40 . 25.0 0.7 50.0 40 . 25.0 0.G 50.0 40.0 25.0 The stains wwt' thoroughly mixed, calcined to cone 5, ground to pass a 200 mesh screen and added to a mat glaze having- the formula, 0.1 K,() ) 0.2 OaO I 0.36 AL<), 1.36 Si<>_. 0.7 PbO J The glaze was then burned to cone 05. The result was a yellow- ish green glaze with blue specks. This was due to the fad that the cobalt was not thoroughly disseminated. A hi uc stain Gov,O a 10 ("ale. A1 2 8 45 ZnO 4o was then made, calcined to cone 7. and ground to pass a 200 mesh screen. Three frits were made using the mat glaze as before. SOME COBALT-URANIUM COLORS TABLE II— SERIES B B i u„ B. Feldspar 17.6 6.3 50.5 11.0 10.0 4.6 10.0 25.0 17.6 6.3 50.5 11.0 10.0 4.6 10.0 35.0 17 6 CaCO 6 3 Red lead Kng'. china clay 50 . 5 11 Tenn. ball clay Flint 10.0 4 6 Blue stain 10 45.0 When applied as glazes, B 1 gave an olive green, B 2 and B 3 rich chocolate browns. These results indicate that the ratio of uranium to cohalt is too high. The next step tried was to use the nitrates of cobalt and uranium, bv Fritting in the mat glaze. TABLE III— SERIES C Feldspar CaCO:, Red lead Eng\ china clay Tenn. ball clay. Flint Cobalt nitrate . Uranium nitrate 17.6 17.6 17.6 6.3 6.3 6.3 50 . 5 50.5 50.5 11 .0 11.0 11.0 10.0 1 . 10.0 4.6 4.6 4.6 3.5 3.5 3.5 10.0 1 2 . 15.0 The frits were ground, and a scries of glazes made by blend- ing with the original mat glaze. Bright glazes were made by adding 20 parts of flint to the frits of this series. The mat glazes were olive green, C, having a bluish shade. Of the bright glazes C 3 was dee]) green in color, and C a and (\, were green witli a bluish shade. SOM E COBALT-1 RANI1 M COLORS Conclusions: Green glazes and ruiats ean be made by blind- ing cobalt iin.l uranium in the right proportions, which is be- tween four ;ui(l five parts of uranium nitrate to one pari of co- ball uitrate. < Vramic Laboratory . University of Illinois. DISCUSSION Prof. Orion: 1 do aot know, whether there has ever been any report made, aboiri the peculiar green developed by one of the roofing-tile plants in this country by the use of eoball oxide and sulphate of antimony. These coarsely ground chemicals were added to a roughly prepared glaze; and the result was thai they succeeded in getting a very passable green. At least it looked like a good green on the roof, but if looked at close by, the size of the blue and yellow spots was so Large as to be offen- sive. The reason, that they did this, was that they were working in a sulphurous close atmosphere, thai spoiled other greens, and they thought, that if they had a sulphate to start with, it would not do any harm. Mr. Uadcliffe: T might say that a man in the berra-eotta business in Kansas told me that In 1 used cobalt and uranium to produce greens. He did not tell me. however, until we worked it out. lie was using it for polychrome work. The cobalt-uran- ium green that he produced was better than any other green that he could make for this purpose. It did no; run or blend off with the white, but instead he could <:"< j t a firm line between the green and the white, or whatever base was beneath the green poly- chrome work'. a3 UNIVERSITY OF ILLINOIS BULLETIN i ssi' i: i) \v i: i: ki.i Vol. XI. .11 I.Y 30, L914. No. 47 [Entered as second-class matter December 11, 1912, at the post office at I'rbana, Illinois, under the Act of August 24, 1912.] BULLETIN No. 23 DEPARTMENT OF CERAMICS R. T. STULL, Acting Director NOTES ON THE DEVELOPMENT OF THE RUBY COLOR IN GLASS BY A. E. WILLIAMS PUBLISHED BY THE UNIVERSITY OP ILLINOIS, URBANA 19 13-1914 Authorized Reprint from Volume XVI, 1914, Transactions American Ceramic Socictj NOTES ON THE DEVELOPMENT OF THE RUBY COLOR IN GLASS BY A. K. WILLIAMS The term •"ruby glass" is applied to red glass colored by the use of copper, gold, selenium and in some cases, flowers of sulphur, the color varying considerably in intensity and shade. In case of copper, the color varies from amber to various shades of reds to brown and to opaque black. With gold the red has a rose tint, and selenium ruby seems to be a brighter red of vary- ing intensities. The red from sulphur is rather unreliable, in that a uniform color is hard to obtain, and therefore only used for lower grades of glass. Copper and gold reds are said to be due to the metals in suspension as colloids. V. Poschl 1 ' describes the preparation of Purple of Cassius from gold, and shows that the red or the purple gold-hydrosol may be obtained, depending upon the proper electrolyte present. Paal s 2 process for the preparation of colloidal solutions shows that a red or blue hydro-sol of copper is obtained, depend- ing upon the properties of the solutions. In G. Bredig's" method of producing colloids electrolytically, he obtained finely divided metallic gold, dark purple in color, when the arc takes place under distilled water. If a trace of caustic soda is added, deep red color is obtained. That copper and gold are in the same condition in glass as in solutions is proven by the use of the ultra-microscope. Zsigmondy 4 says that ruby glass will become red, or remain colorless upon slow cooling according to its quality. It will al- ways remain colorless on chilling, the normal red color generally being brought out upon reheating to the softening point; (high lead glasses show yellow or brown instead of red). The coloring is due to the gold, which is at first homogeneously dissolved in 1 V. Posehl. Chemistry <>/ Colloid 2 Ibid, p. 6G. 3 Ibid, p. G7. 2 DEVELOPMENT OF RUBY COLOR IN GLASS the glass, later separating - out in the form of ultra-microscopic particles which reflect green light. He compares this phenomenon with devitrification, and re- fers to Tammann's 5 work on devitrification. Tammann shows that the speed of crystallization, and the ability to crystallize in- crease with diminishing temperature from the melting point and then decrease again, while viscosity steadily increases. Zsig- mondy applies Tammann's results to ruby glass in this manner: "Ruby glass is worked several hundred degrees lower than its melting temperature. At the working temperature, conceive it as a super-saturated crystalloid solution of metallic gold and the smallest amicroscopic particles to be centers of crystallization, it will at once be seen why ruby glass sometimes remains colorless upon simple cooling. In this case the optimum temperature for spontaneous crystallization is so low that the glass is very viscous and the speed of crystallization reduced to a minimum. If by reheating, the glass acquires a certain mobility, the gold separates out upon the nuclei present which by growth become sub-microns, visible in the ultra- apparatus and turning the glass red or darker." V. Poschl 6 says that gold ruby is obtained by an addition of gold chloride to the glass melt from which particles of gold separate out, when the mass is quickly cooled. These particles, however, have the magnitude of amicrons. so that the glass ap- pears colorless. By heating anew until the glass becomes soft, the particles grow until they attain the size of ultra-microns, to which the cause of the red color is traced. The preparation of copper ruby glass is performed by an analogous method. Copper ruby has, in the past, been made by a process known as flashing. This process is described somewhat as follows by Rosenhain : 7 "Flashing glass is the process of placing a very thin layer of colored glass on the surface of a more or less colorless glass of usual thickness. This is generally accomplished by taking a small gather- ing of the colored glass on the pipe, and the remaining gathering for the piece to be made from the colorless glass pot. When this glass is blown, the ruby glass lies in a thin layer over the inner surface of the cylinder. The special skill required is in blowing this layer to a uniform thickness to obtain a uniform color." 4 Zsigmondy, Colloids and the ultra-viicroscopc, p. 165. 5 Tan. inarm, /.rit. far Ehctro-chimi, 1904, Vol. 10, p. 532. I Ibid I, p. 103. 7 Walter Rosenhain, Glass iianufacturi . DEVELOPMENT OF KIT.Y COLOR IN GLASS 3 The necessity of flashing is due bo tihe density of the color. Copper colors are so dense thai many glasses are opaque when over :! nun. thick, the color depending upon the composition and rate of cooling. However, it is possible to control the density of tlie color gomewhal in the Hashed ruby glass by carefully con- trolling the temperature of working the glass and pate of cooling in the molds. These Factors tnusl be controlled very carefully in practice to produce uniform results. If these glasses are cooled very quickly, as for instance, chilling in water or rolling very thin (2 nun. thick) on an iron plate, the red color will not develop, or at least shows only in scattered streaks. By reheating at defi- nite temperatures, the color may be obtained in varying degrees of intensity from amber to opaque black, depending upon the temperature to which the glass is reheated. Thus it will be seen that the temperature and rate of cooling must be constant, to produce a uniform shade of red when this color is developed during blowing. At the present time, however, copper ruby glass is being made in which the color does rot come out in the pressing or working, but is brought out later by reheating. The density of the color in this glass is very much less than the flashed ruby glass, and pieces of greater thickness can be easily made. The color range from a light amber through reds to a dense opaque black-, with an increasing temperature. Available literature consulted on the subject gave no com- plete or definite methods for working ruby glass, but emphasized the oecessity for care. The following are some formulae and directions obtained: Gerner, 8 gives a history of copper ruby glass and a number of mixes with methods of handling. The following are two of 1 he batches invert bv him : Gei oer, "Gltus," p, 1 95 DEVELOPMENT OF RUBY COLOR IN GLASS GERMAN COPPER GLASS . 100.0 Sand 25.0 Potash 17.0 Borax 2.5 Cu 2 5.0 Sn0 2 0.2 Fe 2 3 2.5 Mn0 2 0.5 Bone ash Calculated Formula 11 0.200 PbO 0.390 K 2 0.120 Na 2 0.095 Cub 0.079 MnO 0.014 CaO 0.0060 Fe 2 3 0.2500 B 2 3 0.0044 PoO, 4.36 SiO, 0.09 SnOo 100 Si0 2 50 Pb 3 4 25 K 2 C0 3 5 NaNO, FRENCH COPPER GLASS This batch is fused, chilled, dried, ground and mixed with 1 Cu 2 0, 1.5 Sn0 2 , 5 cream of tartar. This is melted and blasted one hour during melt. Calculated Formula 0.534 PbO 0.346 K 2 0.074 Na 2 0.046 CuO 3.900 Si<0 2 0.034 SnOo Notes on ruby glass from Sprecihsaial 10 give the following by translation : "In the manufacture of ruby glass it is not in the field of the furnace man to control the color. Repeated fusion and cooling- makes the best color, and the color does not depend as much upon the per- cent of coloring oxide in the mix as upon the temperature of the glass while working, the rate of fusion and rate of cooling the fin- ished piece." The following hatch is given: "The empirical formulae of nil glasses by I lie writer. »° Sprechsaal, Feb. 6, 1913, p. 92. riven in the following work were calculated DEVELOPMENT OF KI'MY COLOR IX GLASS 5 LIGHT RED DARK REM Sand loo.o kg. 100.0 kg. Soda ash 16.0 kg. 16.0 kg. Potash Ki.o kg. 16.0 kg. Borax 4.0 kg. 6 . kg. Whiting 10.0 kg. 12.0 kg. Witherite lo.o kg. lo.o kg. Cu.O 2 . kg. 4 . o kg. S11O2 2.0 kg. 4.0 kg. Fe 2 O a 0.5 kg. l.o kg. Cream of tartar 0.8 kg. 1.3 kg. Calculated Molecular Formula 0.385 Na 2 ] 0.210 K,o 0.222 CaO 0.110 BaO 0.0(54 CuO 0.0066 Fe 2 3 13.63 Si0 2 0.0660 B.,6.. [0.03 Sni) "The manufacture of ruby glass demands great care and practice in working. This is especially so with pressed glass. The raw hatch should be put into a preheated pot and melted six hours. The melt is blasted several times and poured into cold water for remelting and refining. If the pressed pieces are not colored enough they can be reheated. The mold must not be too hot to allow the glass to cool too slowly, or too cold to chill and cause the pieces to crack. The following batch is also given:" 11 Sand 100.0 kg. Potash 25 . kg. Red lead 25 . kg. Borax 10.0 kg. Soda 5.0 kg. Cu,0 3.5 kg. SnO; 3.0 kg. Fe,0 :: o.5 kg. MnO-. 0.5 kg. Cullet 25.0 kg. Cream of tartar 0.5 kg [bid 10, p. 92. DEVELOPMENT OF RUBY COLOR IN GLASS Calculated Molecular Formula 0.2020 K 2 0.6230 PbO 0.1010 Na 2 0.0668 OuO 0.0079 MnQ* 0.00418 Fe,0 : r 0.07250 B.,0. 2.310 Si0 2 0.018 SnOo Rudolf Hohlbaum 1 - says that red colors may be obtained by the use of Cir.O, selenium, sulphur and gold, but is most ofteu obtained from Cu 2 0. He gives the following- batch for a copper rubv : 100.0 Si(X 31.0 K 2 C0 3 16.0 CaCO, 0.6 Cu 2 2.0 SnO, K 2 CO 3 =80 to 85 percent pure Calculated Formula 0.536 K,0 0.440 CaO 0.023 CuO 4.570 Si0 2 0.041 SnO, Hohlbaum says : "Concerning the mixing- of the C112O, I wish to remark that it is possible to obtain the ruby color with 0.4 percent Cu 2 0, also with 0.8 percent. However, with 0.8 percent of the batch as Cu;0 the color is so dense that large masses are not workable. As such a small quan- tity of Cu=0 is needed to make ruby, it is mixed best by using 0.8 per- cent Cu-jO and SnO with half the batch of glass. When the glass is ready to blast then mix the batch containing 0.8 percent Cu^O with an equal batch of crystal glass, and a 0.4 percent Cu^O batch is obtained which gives a weaker color. It is best to employ SnO as a reducing agent to insure the obtaining of a ruby color, and one finds from practical experience that the mix must contain less than double the quantity of Ctu-O as SnO. If this is not sufficient reducing agent, cream of tartar may be used in quantities to satisfy all conditions. Iron scale may also be used as a reducing agent but the pure ruby color is then changed." 12 R. Hohlbaum, Seitgewasse Uerstellung Beatbeitting vnd Verziervng dcs Felnern Holglases, p. 125. DEVELOPMENT OF RUB? COLOB IN GLASS / Hohlbaum 13 gives the following hatch for a gold ruby: Rose Color Sand 100.0 kg. Potash 34.0 kg. Calcium carhonate 17.0 kg. Gold 16.0 gms. Gold must be brought into the mix in a very finely separ- ted form, best in solution or as Purple of Cassius. To get the gold in solution, it must he cut into small pieces and dissolved with aqua regia. The gold solution is poured on part of the mix. and this mixed with the balance of the batch. In the heat of the oven, the decomposition of the gold chloride takes place so rapidly, that a portion of the gold chlor- ide is carried away undecomposed. There is. therefore, not so much gold dissolved in the glass as is introduced, and the color is much weaker than it would he, if all the gold were dissolved. It is, of course, reasonable for one to try and reduce the vapori- zation of the gold chloride as much as possible. This may be done by pouring the gold chloride on 1 kgm. of sand and evap- orating to dryness. Then mix this well with half of the hatch, or use gold purple in the same manner. According to Hohlbaum 's experience, either phosphoric acid or barium work favorably in the making of gold ruby, causing the gold to separate out more rapidly. Without either, the ruby is too light. A batch for making a rose glass with a violet tinge with the use of barium is given. Rose Glass with Barium Sand 100 . kgm. BaCO* 10.0 kgm. 93 percent soda. XaX'0 43.0 kgm. Gold 12.0 gms. Selenium Ruby, Light and Rose Colored Arsenic 200.0 gms. Sand 100.0 kgm. Potash, 80-85 percent ::4 . kgm. CaCGv 17.0 kgm. Selenium nitrate 120.0 gms. " [bid 12, p. 126. 8 DEVELOPMENT OF RUBY COLOR IN GLASS In the reds with sulphur, one should not use the alkali sul- phates, hut only sulphur with charcoal as a reducing agent. The charcoal keeps the sulphur from combining with the soda and potash. In sulphur ruby, a great part of the sulphur vaporizes in the working. The melting glass foams vigorously, and there- fore one should fill the pot only half full at first, and after the batch reaches quiet fusion, put in the second half. Sulphur ruby is hard to make in uniform colors, and dark- ens in the muffle. It is not used for making higher grades of glass. Two batches for sulphur ruby are given : Xo. 1 No. 2 Sand 100.0 kgm. 100.0 kgm. Soda 45.0 kgm. 45.0 kgm. CaCO.3 20.0 kgm. 20.0 kgm. Flowers of sulphur 7.0 kgm. 10.0 kgm. Antimony sulphate 5.0 kgm. Charcoal 2.0 kgm. EXPERIMENTAL DATA BY WRITER The foregoing typical batches for ruby glass are but a few of a large number given in the literature pertaining to glass making. An examination of these shows a wide variation in com- position, but all agree in that they are high in silica and contain tin. In copper ruby, the amounts of copper and tin vary widely in their ratios to each other. These copper rubies are probably used in the manufacture of flashed glass. In the beginning of the following experimental work, sam- ples of commercial copper ruby, both the quick-cooled colorless and ruby colored were obtained. The uncolored sample was broken into fragments, and different fragments were heated to different temperatures for various lengths of time. A small lloskins electric furnace was used, and temperatures were read with a Leeds Northrup potentiometer, using a platinum, plati- num-rhodium thermocouple. DEVELOPMENT OF RUBY COLOR IN GLASS The following results were obtained: TABLES PIECE MAXIMUM TEMPERA- TIME HELD AT MAX. REMARKS TURE TEMP. °0 minutes 1 500 30 No change in color 2 500 60 No change in color 3 550 30 No change in color 4 550 60 No change in color 5 575 1 No change in color 6 575 30 No change in color 7 600 1 Very light amber 8 600 15 \ cry light amber 9 600 30 Bright amber, slightly darker than No. 8 10 600 60 Bright amber, same as No. 9 11 650 1 Bright amber, same as No. 9 12 650 30 Deep ruby, edges slightly soft- ened 13 650 60 Same as No. 12, edges slightly softened 14 675 15 Same as No. 12, edges slightly softened 15 675 30 Same as No. 12, edges slightly softened 16 675 60 Darker than No. 15, edges slightly softened 17 700 1 Same as No. 10, edges slightly softened 18 700 30 Dark red. edges slightly softened 19 900 30 Grayish purple, opaque, softened out of shape The rate of increase of temperature was a constant factor in all of the-e tests, a.s follows: ten minutes from room tempera- ture to 300°C; 300°C to 500°C at rate of 50° per minute: 500° C to maximum temperature at a rate of 25° per minute. The results seem to show that the color at any definite tem- perature is practically constant, and that the color change at that temperature is apparently instantaneous. However, time is 10 DEVELOPMENT OP RUBY COLOR IN GLASS required for the temperature to even up through-out the thick- ness of the piece. It will be noticed that the glass shows signs of softening at that temperature at which the strong color develops. This is probably the softening point Zsigmondy 14 refers to in the article previously quoted. It is observed that there is little or no ap- parent change in color brought out between 650° and 675°, giv- ing a safe range for an annealing oven. Most of the glass formulas observed were high in lead and in silica. Accordingly the following formula was selected, it being the upper silica limit for most glasses : 0.5 PbO j 0.5 Na 2 } 3 Sl °: In order to determine a suitable method of working, several small batches of this glass were fused. The method adopted was as follows : The glass was fused in Battersea crucibles in a small pot furnace using gas and compressed air. The temperature range required for firing and to make the glass liquid enough for pour- ing, was between 1480°C and 1520 C. One-half hour was taken for complete fusion of the lead glasses and one hour for the lead- less glass&s. Not much trouble was experienced in reducing the copper oxide and preventing oxidation. Although a slight reducing flame was used, the presence of cream of tartar (about \/% per- cent) seemed to make reduction certain, if the time of heating" was not too long. When fusion was complete the glass was poured on a heavy cast iron plate 1 in. thick, and then rolled to a thickness varying from 2 to 5 m.m. The thinner portions usually cooled colorless, and the color developed in the thicker, slower cooled portions, i. e. turning red or opaque brown or black. 14 Ibid 4. DEVELOPMENT OP RUBY COLOR IN GLASS 11 w = o o n i- _ ** c © © © o © © us co -< o o o »n O O O co O © © 'oooowoo CO O O © O O i-h © lO CO 02 © © © m < ? en © © © CO O © © © © © © CO © © IN © © © © © tH © Ifi :- 0! o © © w © © © CO © © © CO©©"* © © © © © © © i-H © Ifl CO O} © © © 'O © © © CO © o © © © ■ © • t- © © o • © © © mm • © © LO c © -co © © m © © . © © t~- © CO © © • © © © © mm • © © © m © © • CO © © o © © . © i-i t- © IQ © © •©©©■© mm • © © © m © O • co S © © Z © © ■ © oj i- o © © • © © © © I ' mm • © © © m © s -co © © © © © .©-+■©© © © • © © 1-1 © mm • © © © m © © -co © © © © © • © -t< -v © CN © © • © © © s mm •©com © © • CO © O © © © • © -r -p © H mm -©com o © -co © © © . .4-1 V \c H c ■7 s u U ©COCO!© © C © t- m c M :: c c c C m • -f ~ S © c _ CO :-. — -• o • © © © r- m c CO • CO © - © t- © m • rt< ~ © © © iH CO • CO 1-1 © © © © C i-i © © © © CO © C © 02 © © © m © © © c c © c © i-< © o o © CO o © 00 02 o © ih m o © © c © © O © T-l c © © © co © © m oi © © co m o o c © © © © o o CO © © © 02 © © i- m © © © © o © C © i-i © © c >- © 1# © © ." — "~. ~ — - 5 pl, > u fc U x u o 12 DEVELOPMENT OP RUBY COLOR IN GLASS SERIES A Glass batches were then made corresponding to the for- mulas given in Series A. The following results were obtained : Number 1 — Colored out very dense opaque grayish-brown color. Number 2— (Decreasing the coloring agent.) This poured well, and cooled practically coloiless at 5 m.m. thick. Softened out of shape at 675 C and colored out, streaked with reddish color. At 700°C. it became dark brown, opaque and still streaked, very soft. Number 3— (Ircreasirg tin to harden.). This poured well and was colorless except for a pale greenish-yellow color at 5 m.m. thick. Heated to 480°C, gives amber color. Heated to 525° C, gives deep red color. Heated to 700° C, softened out of shape giving a dense, brown opaque glass. Color change very rapid. Number -1— (Decreasing the Cu 2 to reduce intensity of color). Color developed darker than No. 3 in pouring, having a greenish cast. Heated to 600° C, its color was deep opaque, and nearly black, amber at 550°C, and brown at 575°C. Number 5 — Developed a rather intense brown color while pouring. Thin colorless sections gave a deep greenish brown at 550°C. and a dense opaque black at 600°C. Number 6— (Still reducing amount of coloring matter). This glass poured clear and colorless. On reheating it changed to opaque black from 550°C. to 600°C. Color change very rapid. Number 7— (Coloring matter left out to test purity of ma- terials for iron). This glass on reheating at various tempera- tures gave no change in color. The conclusions from this series of glasses, (excluding No. I) 15 are: (1) Dow amounts of copper seemed to increase the density '■'This glass w;ts not melted well enough to judge results. DEVELOPMENT OF BUB'S COLOR IX GLASS L3 or opacity of the color, and decrease the signs of red, giving greenish browns. 2 An increase in the tin in No. 3 st pped the streakiness >ho\vn in No. 2. 3 Glass No. 3 was the best glass in scries A. giving a color ess glass when poured and cooled quickly. Reheating showed shades of good vril at various temperatures. However, the color change is so rapid, it would be difficult to control uni- formity of color. SERIES Al Series A, was constructed in order to obtain harder glasses than those in series A. by replacing PbO with CaO so as to raise i licit- temperatures of softening-, and to determine how this af- fects the range of color change. Glass Xo. 1 of this seiies show imI a dark brandy color on pouring, coloring out quicker than Xo. 3 series A, which con- tained the same equivalents of Cu and Sn. This glass did not soften out of shape on reheating at 700° C, as did glass No. 3, series A. but gave a dense opaque color. If it could be handled, without coloring- in pressing, this glass gives a good transparent red at 5 m.m. thick, upon reheating to the proper temperature. • ilas^es Xos. 2 and 3 (reducing Cu 2 0). Colored out quite dense, on pouring becoming nearly opaque. When reheated above 600°C. the glass turned a deep opaque purple. Glass Xo. -4 (reducing Sn0 2 ). This glass seemed to color out as rapidly as Xos. 2 and 3. The conclusion which may be drawn from this series is that the rapidity of precipitation, or growth of color is increased, in- stead of decreased, as would be expected by hardening the glass. SERIES B The basal formula for Ibis scries i^ one of the published formulas given in Sprechsaal. 16 It is a high lead low silica glass, containing some boras and is a much softer glass than series A and Al. 14 DEVELOPMENT OF RUBY COLOR IN GLASS M s o m «: »T "• 5 S> © © © c c © © s c © C © © © © u o ■c* «)0« c - © © © c © ~ - c © © o CM --0 « co co CO CO CO CO t- £- l- f~- 1- V- f~ r- *^- f- M © o c c c © © c c C c c c C © o o c r © © © c c C c c c © © CM CM c © c c ~ c c co o a > r > c © 3C c o © © © © c © O « © sc «r "* 0- J- t- © C © a o o c > c 5 C © c C © © © © © c c o c c > c ) c ) © c c © © © © © © c HMr H P 3 C 3 CO r- a ^ CO CC CC CO Pt fC CO o 00 CO c j a 3 C 3 CO C c ; co co co co co co co 02 CM CM t> ! c\ ! C\ 1 CM Q o ! cm e ! CM CM CM CM CM CQKP J o } O i > o ! (M W O! M H N N o o o c 3 C 3 C 3 © C > c J © © C © © © © ;> W «t> I o I C ! CM C\ ! O ! CM CM CM CM CM CM CM o o c 3 C 3 C 3 © C ) c 3 © © © © © C © O CO t- c 3 r- • r- ■ t- CT ; r- • t> t- t- t> t- !> J> cm cxf o ! O ' o '. CQ G\ c ! CM CM CM CM CM CM CM Ch OfflS 3 5£ 3 « 3 © « > « 3©©©©©©© o o c : c 3 C 3 © C > c 3 © © © © © © © o rlCdr H 1? } )Nr h a 3 © © 00 CM CM CM CM O O C 3 C - r 3 © C > i- H N CO CO CO O O O 3 T-l r-< r H i- HiHT-IOOlHi-li-l © © c 3 C 3 C 3 © C 3 C 3 © © © © C © © CO H«C T h u 5 © fr • a 3 CS O H M CO * If) l-H tH l-H i-H ^H i— i J Zl ^ DEVELOPMENT OF RUB'S COLOR CN GLASS 15 The results showed this very markedly. The fusions, made at the same temperature range 1480 C and 1520 C, were more fluid and poured easier. Numbers 1. 2. •'$ and 4 developed deep opaque glasses when poured 4 to 5 m.m. thick. The thinner portions, however, in- creased in degree of transparency to about 2 ni.ni. at which thickness the glasses cooled colorless, hut of course vrvy brittle. Upon reheating, the colorless pieces of these four glasses colored to about the same color density when heated to the same tem- perature. At 500 0, they showed an amber color changing to a light red at 525°C, and to a ruby color at 550 C, becoming opaque at 600 ('. Leaving out the iron, or manganese or both, (especially the latter), seemed to improve the quality of the red and to give a less dense color. This type of glass gives a much better red color than any of series A, but it is impossible to work with sections as thick as commercial glass pieces would be made and still obtain a transparent color. However, it would work as a ruby glass in making Hashed articles and give a good color. Manganese dioxide and Pe 2 3 are detrimental rather than helpful in obtaining good colors. In series B, Numbers 5, (5 and 7 (in which SnCX is absent), the glasses were more opaque in all cases. Number 7 colors out even in the thin sections to a dense black. In glasses Xos. 8, 9. 10, 11 and 12, the tin was kept constant ami the copper varied. In all cases the tendency was to increase opacity and the rapidity in which the color appeared on pouring. In glasses Xos. 18. Id and 15, in which the tin was increased, no beneficial results were obtained, since these glasses were more opaque than the preceding ones in the group. The ruby color in glasses as soft, and as low in Si0 2 as the members of this group cannot be controlled. However, when Bl and B2 were melted, quenched in water and remelted, there was an improvement, since all signs of streakiness disappeared, and the color became verv uniform on reheating. 16 DEVELOPMENT OP RUBY COLOR IN GLASS PS < a j-j»n©T-i»ot-©-*-*-t< co ro co ro COCOCONNHM'tCOCOCO g< M (N M M « « (M W CO O -t « « W W ro co co co c— 1 i— 1 iH i— 1 COCOCOt-COOOlHCOCOCO HrtHHiHNiHrlHHH X - o © © © ©©©©©©©©©©© s a o © © © CO CO CO CO ©©©©©©©©OC© cococococococococococo © © © © ©©©©©©©©OC© to © © © CI N IT! « ©o©©©©©©©©© W 0! (N CM 0! CM CM CM CM CM CM E* 3 © © © © © © © © i-H i-l rH i-H ©©©©OCOC©©© ©o©o©©©©©©© t—It-It-ii— ItHi— li-Hi— li— ii— ii-i o H « CO-* 0©t-COC51©i-l(MCO^>-0 1-H rH T-l 1-H i-i 7-1 DEVELOPMENT OF Rl'BY COLOB IN CLASS 17 The basis of this series obtained from Hohlbaum 1 ' is en- tirely different than series B. li is a lime-potash, high silica, Leadless glass, with high tin, therefore, a comparatively refrac- tory and viscous glass at low temperatures. One hour was taken for fusion. Hohlbaum's hatch calls for SnO as the reducing agent, cream of tartar being added ,-is a precaution to insure sufficienl reduction. Number C-l was first made by substitution of SnO. for SnO, and leaving out the cream of tartar. An oxidized clear colorless glass was the result, giving no color change when reheated beyond the softening point. Number C-I was again made using SnO. and 0.5 percent cream of tartar. This glass was exceedingly viscous and quickly cooled below the point of easy pouring. Upon pouring and roll- ing, (although taking a little more time), no color change took place, the glass remaining clear and colorless. I 'pon reheating, no color change took place until 800° C. was reached, when a light amber color was obtained, 850 ( !. gave a pale reddish brown, 900° C. gave a light brown, 1000 C. softened with an opaque brown color. The red color was not good in this glass and it seemed to be entirely too refractory. Series C, Xo. 2. (Reducing Si0 2 to soften). This showed an improvement in the working qualities with no tendency to color out on pouring. Reheating this glass gave the following results: 800°C. a distinct light red, 850°C. a good ruby color, !»oi) C. a deep dark red Dearly opaque when 4 m.m. thick. Series C, Xo. 3 (reducing Si0 2 still further) gave a fusion which poured colorless and flowed freely. Reheated to 850° it showed a reddish brown, slightly streaked. 900° showed a dis- tinct deep brown. 17 Ibid 11, p. 12">. 18 DEVELOPMENT OF RUBY COLOR IN GLASS oooococooooc c © c © © © M C! i-H ooooooooocco ©o© ©©©©©©©©© Ci C2 C5 Ci CI C! C! CI C! CJ CJ c> ©ocoooc©©©©© ©00©©0©0©©©0 ©ooocoooooo© ooocoocoocco (OtOtD(DtOtO(COtDO!DO ocoooooooooo CQTtiTj'Tt'-t-^-Th^f Hf)ro-fin»^aioo r c oocoocoocccc ««««««nww«ejw X S pa < - 1" c; c; *o • • ic c' DQ Tf ^ ^ "^f "^ ^ ^t* ^t* ^f ^ "3" ^ o MMMNS««KWW«W tHi-Ii-It-ItHiHi-Ii-ii-It^«-iiH o 00©0©tJ<->*<©©©00 iMwoiNNt-t-'nw'nmio < E- o p. ooooooooocoo ooooooccoocooocooooooooo COCOCO©SOOSD©0©OSD E- 3 fc. coooooocoooo O'OooiHoomm'O'OOO ©t-mcocjot-t~j— t-o© flHrirlrHWHmHrtWW o HRminniot-KOOHej DEVELOPMENT OF RUBY COLOR EN GLASS 19 Series C, No. 4 (less Si0 2 than C3). Poured clear and col- orless but when reheated to 850 became more streaked and .showed a more decided brown. Series C, No. 5, poured clear and colorless as the others, bu1 .showed brown streaks. When reheated to 800 it showed a very streaked brown color. When the glass was remelted and re- poured it gave a very clear glass. I '[ton reheating this to Toil ('. the color came out a clouded black, increasing in intensity with the reheating temperature. The foregoing five glasses in group C show that: (1) Reducing the Si0 2 from 4.o7 to 4.0 molecules improved the color in this series. Further reduction, however, changed the color to browns and then blacks, giving about the same range of brown and blacks with 3 Si0 2 as series A gave, having 3 SiO., and small amounts of copper. 2 i High silica seems necessary in order to develop a good red color. The color change takes place at rather high tempera- tures for a reheating furnace, and the glass appears to be too viscous for good working properties. Glasses 06, C7 and C8 were made by introducing PbO in place of part of the CaO with the idea of softening and. if possible, still retaining the property of not coloring out on pouring. C6 and C7 in which 0.2 PbO replaced 0.2 CaO showed a dis- tinct improvement in the working qualities and uniformity of color, although these glasses colored out in the thicker portions during the pouring; C6 to a light red and 07 to a deep ruby. These glasses, however, were transparent to a thickness of 8 ni.m. in comparison with series B, which were not transparent in pieces over 2 ] 1 . m.m. in thickness. Reheating clear portions of CO gave a good, deep, ruby color at 650°C, a considerable lowering of the temperature over the leadless glasses for developing color. This g!ass also has a fairly constant color over a temperature range of 25°C (625° 0. to 650°C). Series C, No. 7 colored out at 570° to the same shade as C6. 8eriesC,No. 8 (Reducing PbO to o.l with 4.00SiO 2 ). This glass gave evidences of being harder than the previous Li'lass 20 DEVELOPMENT OF RUBY COLOR IN GLASS (C7) as the fusion colored out a very little clearer at 6 ni.ni. thick (similar to C6), and the color. ess portions gave a deep clear ruby on reheating to 570 : , the same as C7 and about 60 3 lower than C6. This glass gave the clearest and best red ob- tained in the foregoing work. Series C. No. 9 (in which 0.1 PbO was replaced in C8 by 0.1 Xa.,0 as borax) gave a glass considerably more fusible, and flowed well in pouring. A very streaked, nearly black, color de- veloped in portions over 3 m.m. in thickness on pouring. Thin transparent pieces heated to 75<> gave a red color, streaked with opaque black lines. This fusion, therefore, did not give good results. The possibility of spoiling the color by over-heating is ever present. It is possible that less B 2 3 would give better re- sults, though this was not tried. Series C, No. 10 (0.1Na 2 O replacing 0.1 CaO). The result- ing glass was clear and colorless, showing a very few light red streaks. The working properties of the glass were very good, especially in pouring and cooling. On heating to 700°C the glass turned a clear light red. 625° C. showed a clear light red. 725° C. showed a clear light red. The color range of this glass is therefore good. Scries C, No. 11 (O.lPbO replacing 0.1 CaO and with 4.57 Si0 2 ). Results from this glass were a failure as the fusion was incomplete and very viscous and colored out a dense opaque black on pouring. If properly fused, better results would no doubt have been obtained. Series C, No. 12 (0.1 Xa,0 replacing 0.1 CaO and with 1.57 SiO„). This glass gave a very good fusion, but was rather vis- eons and showed no color on pouring. Heating this glass to 700° C gave an amber colored glass streaked with dark red lines. At 800 C C it showed a good even ruby color. The conclusions from this last series of glasses (C6 to C12) are (1), that soda replacing lime softened the glass without causing the color to come out in cooling. (2) Lead on the other hand caused these glasses to color out rapidly on cooling, but did not make them opaque. DEVELOPMENT OK RUBY COLOR IN GLASS 21 General Conclusions. The following are general conclu- sions one may draw from this work regarding the composition of a workable ruby glass. A workable ruby glass is one which will not color out when eooled at the rale obtained in the press- ing process, and yet will give a workable range of temperature for reheating to a uniform color at temperatures below 700°. 1st. Highly fluid glasses will color out rapidly, viscous glasses slowly. 2nd. Replacing lime with either lead or soda, increases the rapidity of color development, lead more so than soda. 3d. High SiOo is necessary for good color, low Si0 2 gives a tendency towards brown or black, and opacity. 4th. High SiOo (4.0 to 4.5 mol.), is necessary to give suffi- cient viscosity. 5th. With high silica, lime-potash glasses the tendency to streakiness increases. Small amounts of lead reduce streaki- ness. 6th. The glass giving the best color in series B is No. 4. Glasses Xos. 1, 2, 10 and 12 of Series C, most nearly approached the requirements of a good ruby glass. They could all be poured without the color developing, and on reheating, the color devel- oped at favorable temperatures. Glasses Nos. 6 and 8, Series C gave the most transparent colors. 7th. Iron and manganese are detrimental to a good red color. 8th. Remelting improves the uniformity of the color which indicates that streakiness is due to lack of homogeneity. 9th. Density of color is apparently increased with an in- crease in temperature. Time is evidently not an important fac- tor in this case. DISCUSSION Prof. Silverman: There are a number of points in Mr. Williams' paper about which T wish to inquire. In the first place, he speaks of the coloring out in the high-silica copper rub- ies. I should like to ask whether Mr. Williams found any direct bearing by the alkali content of the glass. There is a claim 22 DEVELOPS ENT OE RUBY COLOR IN GLASS made at present that a copper ruby can be manufactured, which is a ruby, out of the pot. I believe his views correspond with mine in that the red color produced is due to high alkali in the glass. In other words, the glass colors out while cooling in the mold, or even earlier., Then as to tin as a reducing agent, I can corroborate these statements also, having had the experience that tin alone in connection with copper gives a rich color, while with manganese and iron the color is off. Tin has to be con- trolled very carefully. If you get below a certain point you obtain a glass which does not color sufficiently; and if you go above you get what is called clouding or a livery color. I would like to ask. to what Mr. Williams attributes lack of uniformity of. color; and whether he feels that a melt over a short duration, like thirty minutes could give a homogeneous glass. Mr. Williams: To answer the last question first: the uni- formity of color in my glasses was not obtained in the first melt. There were signs of streakiness at first, but upon remelting, good clear colors were obtained. It is probably the mechanical handling of the glass, or the duration of the melt which has a tendency to make the glass cloudy or clear. The first question you asked, regarding the high alkali con- tent, I did not quite understand, however I will make this point, that when I used lead, replacing the alkali, it caused the colors to come out more quickly in the handling. The color was just as good, in fact a, little better, but density of color could not he controlled. Lead improved the uniformity of the color but gave a tendency toward opacity. If you do not want the color to come out during pressing, it is necessary to keep away from lead. Prof. Silverman: I should like to know further, what the object is in trying to prevent the color from coming out during pressing. Mr. Williarks: If you do not prevent it, the different var- iations in the cooling of the mold would not give the same shad- ing of red in the finished pieces. Prof.. SilnrnKin: But do you not get, the same effect by heating to a certain temperature afterwards? DEVELOPMENT OF UIT.V COLOR IN GLASS 23 Mr. Williams: Fee; bu1 can you control the rate of cooling of glass in the mold sufficiently accurately as to give uniformity of color from piece to piece .' Prof. Silverman: 1 cannol quite see bow that lias a bearing mi the rate of cooling. Suppose your glass does ool color out below 700°. You mighl have a mold anywhere from 400 to 600 , and the fact that you have no color would be oo indication thai your mold temperature is correct. In other words, you have .such a largo range below the coloring-out temperature that it dues not seem any better indication as to mold temperature, than if you had a glass that colored out, except possibly to tell you that the mold is too hot. Mr. WiUiams: My experience with glass that colored ou1 was that glass of various thicknesses was different in shade. Tin? difference in temperature of a mold would influence the color. 'The coloring out at a definite temperature also depends upon the speed at which a glass cools through the small temperature range of color development. If the glass cools at a high rate of speed through this temperature, the colloidal copper would not come out in large enough particles to show color. If the cooling rate is slower the particles grow of sufficient size to give color. Mr. Gelstharp: I should like to ask whether that was not sub-oxide of copper. Mr. WilUams: I used cuprous oxide. Prof. SI nil: Perhaps I might throw a little light on Prof. Silverman's question by stating, that among the things .Mi-. Wil- liams is investigating is a study of the temperatures at which the copper ruby comes out, and the effect of length of time as well ;is temperature in bringing it out. That is why he is trying to secure colorless glass to begin with.