THE ANALYSIS OF PARIS GREEN 
 
 BY 
 
 EDITH FIELD CLOYES 
 
 THESIS 
 
 FOR THE 
 
 degree OF BACHELOR OF SCIENCE 
 
 IN 
 
 LIBERAL ARTS AND SCIENCES 
 
 COLLEGE OF LIBERAL ARTS AND SCIENCES 
 
 UNIVERSITY OF ILLINOIS 
 
 1922 
 

 
 
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Table of Contents. 
 
 I . Acknowledgement • 
 
 II. Historical. 
 
 III. Description of method used. 
 
 IV. Part II. The Ratio of Potassium Iodide to Copper in 
 
 the lodometric Method. 
 
 V • Experimental . 
 
 VI. Conclusions. 
 
 VII. Bibliography. 
 

 
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Aclmov/leelgement 
 
 The writer wishes to express her appreciation for the 
 inspiration and helpful suggestions received from Dr.G*D* 
 Beal^ under whose supervision this work has heen carried 
 out. 
 

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 Historical, 
 
 During the last decade, work on the analysis of Paris Green 
 and similar insecticides and fungicides has been pursued with 
 greater diligence, due in part to the inrestigations stimujr 
 lated by the AssocAation of Official Agricultural Chemists* 
 
 The Sureau at Washington sent out calls for work on this com- 
 pound to many experiment stations, with the result that serera; 
 methods for its analysis, or for the ascertaining of both the 
 copper and arsenic content thereof, were brought forward* The 
 following are some of the most important of them: 
 
 j. 
 
 Hedges’ Method for Arsenious Oxide in Paris Green. This 
 method calls for a 2 gram sample which is dissolved in 50 cubic 
 centimeters of (1:1) hydrochloric acid, at a temperature not 
 to exceed 80° Centigrade, when dissolved; the solution is made 
 up to 250 cubic centimeters with watery then 25 cubic centi- 
 meters of this are taken, and made up to a volume of 300 cubic 
 centimeters, when an excess of sodium bicarbonate is added, 
 and the solution titrated with twentieth normal Iodine solutioi , 
 C.M. Smith Method for Arsenious Oxide in Paris Green. A 2 grar 
 sample is treated with 50 cubic centimeters each of water and 
 (1:4) sulphuric acid; after solution^ water is added to make 
 250 cubic centimeters of the solution; then 25 centimeters of 
 this are taken and diluted to 150-200 cubic centimeters, when 
 it is neutralized with sodium bicarbonate, 10 grams in excess 
 added, also 5 grams of ammonium chloride, and then it As tit- 
 rated with twentieth normal Iodine solution* 
 
 Various comments for and against these methods have been 
 made by different analysts, for example, - 
 
 E.R.Tobey:”! much prefer Hedges* Method to the C.M. Smith or 
 
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 eren the official methods*” 
 
 S*D.ATeritt Results show one method as good as the other. 
 Leare it to the choice of the worker.” 
 
 0. B.\?inter : ” smith and Hedges* methods are quicker than the 
 official method, hut they rim slightly lower.” 
 
 J.J.T. Graham and F.L. Elliot prefer the Smith method to that 
 og Hedges as there is no danger of losing any arsenic when 
 Paris Green is dissolved in sulphuric acid; whereas when hydro 
 chloric acid is used, the temperature must he watched oarefull 
 or the arsenious chldride is lost. The results do not check as 
 well as might he expected, hut this is due in part to ©rrors 
 in standardization of the Iodine solution. The results with 
 Hedges* method run slightly lower than those of the official 
 method, hut it was found that if the temperature was lowered 
 the results were better. Smith *s method also gave lower result 
 
 Both methods are easy, quick, and accurate for determining the 
 
 arser.iou^: oxide, hut not applicahle for deterraining the 
 
 total arsenic where a part is in the form of the arsenate. 
 
 The use of sulphuric acid instead of hydrochloric acid in 
 the official method has the following advantages: 
 
 1. There is no danger of losing arsenic as arsenic tri- 
 chloride. The reduction of the arsenic oxide to assenious 
 oxide is always complete, and better agreeing results are 
 given, with less care in manipulation. 
 
 2 . 
 
 Less acid and potassium iodide are needed here, so that 
 it is a cheaper method, and less time is required for 
 neutralization. 
 
 The method of determining arsenic by distillation with hydro- 
 chloric acid is very accurate. The Referee, R.C. Roark, recom- 
 
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 mended that these methods he adopted as official, and that the 
 present official methods he discarded. 
 
 R.C .Roark regards the distillation method as hy far the 
 most accurate. Several distillations can he made at the same 
 time. The distillate can he kept any length of time. The arsen- 
 ic can he determined in hoth forms and separate from antimony. 
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 approximate analysis, hut their use is limited, and the arsenic 
 is determined only as arsenious oxide. 
 
 3 
 
 O.B. Winters, of the Michigan Agricultural Station, reports 
 work there on the determination of lead, copper, zinc, in such 
 mixtures as Bordeaux-lead arsenate, zinc arsenite etc.; and a 
 comparison of the Gyory-Bromate method with the officiiil Iodine 
 method, for determining arsenic when present in hydrochloric 
 acid solution. The results obtained \yith the Gyory method were 
 promising. Moreover good results were also obtained with the 
 distillation method of determining the total arsenic in London 
 Purple. 
 
 J.J.T. Graham tested out several methods and made the 
 following reports: the Bromate method for the determination 
 
 of the total arsenic is carried out ini the following manner: 
 proceed as directed under the official distillation melthod, 
 until the distillate is made to a liter in volume. l.Take ali- 
 quot parts of 200 cubic centimeters, heat to Centigtrade, 
 and titrate with standard potassium bromate solution, tising 
 methyl orange as an indicator. 2. Proceed as in (1.) except the 
 titration is made without heating. The number of cubic centi- 
 meters of standard bromate solution used, times 2 equals the 
 
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 percent of total arsenic in the sample as expressed in arsen- 
 ious oxide. The iodate method: proceed as under the distil lati 
 method, except the distillate is made to a rolume of 600 cubic 
 centimeters. Transfer 100 cubic centimeter;; parts to glass 
 stoppered flasks, add 5 cubic centimeters of chloroform and 10 
 cubic centimeters of hydrochloric acid. Titrate with standard 
 Iodate solution until the iodine disappears from the chloro- 
 form when thoroughly shaken. 
 
 Graham said that both methods checked closely, but that 
 the reaction was slower in the cold Bromate method, while the 
 hot method here is very satisfactory, ihe Iodate method gives 
 accurate results, but the manipulation is not so smooth and 
 easy as in the Bromate method. 
 
 O.B. Winters reports that he has tried out the following 
 methods; Gyory-Bromate method: where one proceeds as under the 
 official Iodine method except that the distillate is made to 
 500 cubic centimeteEs instead of a thousand, a) Transfer a 100 
 cubic centlmeterr, parts to flasks* Heat to almost boiling and 
 and titrate with standard Bromate solution using methyl orange 
 as an Indicator, b) Same as a except the solution is n4t heatec 
 
 Iodate method: This is the same as the Jamieson method. To 
 100 cubic centimeters of distillate add 6 cubic centimejrers of 
 chloroform and 10 aibic centimeters of concentrated hydrochlor- 
 ic acid, and titratefwith standard Iodine solution. 
 
 Winters says howelrer, that although the results obtained 
 with this method are good, thevprocedure is too long and the 
 technique disagreeable. The hot Gyory-Bromate method is good 
 and very convenient but a maximum temperature should be stated 
 
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 here. The cold Bromate method runs too high, as the indicator 
 is not sensitlre enough in cold solution. 
 
 A few other metho( s that hare been suggested by chemists 
 other than those reporting to the Association of Official Agri- 
 cultural Chemists are as follows: 
 
 Oxalate Iodine process for Paris Green Analysis by C.H. 
 
 u 
 
 Peters and L.F. Fielding. Oxalic acid gires a quantitative 
 separation of eopper from arsenic, the copper being precipitat- 
 ed as the oxalate; A .25 gram sample is boiled with less than 
 
 1 cubic centimeter of (1:10) sulphuric acid in a total volume 
 of 50 cubic centimeters, and while the solution is still hot, 
 
 2 grams of oxalic acid crystals are added and the heating con- 
 tinued. Allow the boiled solution to stand over night and then 
 filter. The precipitate is dissolved in water with sulphuric 
 acid, and titrated with potassium permanganate. The arsenic is 
 determined by titration of the filtrate with Iodine solution 
 with an excess of sodium bicarbonate present. The results 
 obtained with this method agree with those of standard methods. 
 
 S.S. Jamieson's method for the determination of arsenic in 
 insecticides has several arguments in its favor, and trivalent 
 
 ate 
 
 arsenic can be^determined tliis way. A solution in eleven to 
 twenty percent hydrochloric acid is titrated with potassium 
 iodate, using a layer of chloroform as an indicator. This 
 method has its advantages over the iodometric method in that 
 a standard solution of potassium iodate is prepared by weighing 
 and dissolving to volume, no further standardization being 
 necessary. The solution is fairly stable, and the results 
 obtained by using this method check with those of other methods 
 
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6 . 
 
 Method Used. 
 
 After yarlous experiments with new methods the results of 
 the following method were found to check closely with those of 
 others. A .5 gram sample of Paris Green is dissolved in 10 cubic 
 centimeters of concentrated ammonium hydroxide, and the solutioi 
 made up to .6 normal; then hydrogen sulphide is passed into the 
 evacuated flask containing the solution, thus precipitating the 
 copper as the sulphide, while the arsenic will remain in the 
 filtrate as ammonium sulfo-salts. A complete precipitation 
 must he made. The solution should then he filtered quickly under 
 vacuum, as the sulphide of copper is quickly oxidized hack in 
 the presence of air. The filter paper containing the copper pre- 
 cipitate is digested with corct^nlrc-.tec!, nitric acid, and the sol- 
 ution heated to drive off nitrous firaes after which hraniine 
 water is added to insure complete oxidation of remaining nitrous 
 acid, after which the copper is determined hy means of the 
 usual volumetric method with tenth normal sodium thiosulphate. 
 
 .he filtrate containing the ctrsenic is heated to d±ive off 
 the excess hydrogen sulphide, after vdiicli the solution is neu- 
 tiralized with concentrated hydrochloric acid, and then made up 
 to a (1:1) acid concentration with hydrochloric acid, placed on 
 the steam b«th, and oxidized with potassium chlorate toa bead of 
 sulphur xo this oxidized solution potassium iodide is added, 
 and the solution titrated with tenth normal sodium thiosulphate, 
 after which it is neutralized with sodium hicarhonate, an excess 
 of 10 grams added, and then titrated with tenth normal iodine 
 solution® 
 
V I. '-^^1 .1' 
 
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7 
 
 Part ri. 
 
 xhe Ratio of Potassiurii Iodide to Copper in the lodoraetric Metho^ . 
 
 In connection with the work on the io dome trie method of de- 
 termining copper this prohljia suggested itself, as to whether 
 or not the same amount of iodine was liberated when cuprous 
 iodide was precipitated on the addition of potassium iodide, or 
 when the precipitate formed dissolred when an excess of potass- 
 ium iodide was used. 
 
 ^^ith regard to this subject Peters says in his paper, that 
 it has been suggested by Bray and Mciiaj? that failure of stand- 
 ardizations to check , may be due to adsorption or solution of 
 some of the iodine by the precipitated cuprous iodide, with the 
 result that a too low titration value of the sulphate is given 
 aagner agrees that the standardization of tnio sulphate by 
 iodates in acid solutions is accurate He found that the con- 
 centration of potassium iodide made no difference and the theor '■ 
 of adsorption did not hold good, but the concentration of 
 potassium iodide should be high it comparison to the equivalent 
 of copper present. The most important point is that the concen- 
 tration of iodide be high in relation to the final volume at 
 the completion of the titration- This point was developed by 
 Gooch and Heath. Tliey claimed that the accuracy of results ob- 
 tained oy the iodide method is affected by (a) varying concen- 
 trations of mineral acids, (b) by the presence of salts both 
 independently of anci in conjunction with acetic and mineral 
 acids. 
 
 ticClure states that cuprous iodide will be precipitated and 
 
 iodine exactly proportional to the ammount of copper present 
 will be liberated, and be held in solution in the excess of 
 

8 
 
 potassium iodide. 
 
 In the present experiment a standard solution of chemically 
 pure copper sulphate solution was made# and aliquot portions of 
 10 cubic centimeters were used* These were made acid with 5 cubi 
 centimeters of acetic acid and varying amounts of potassium 
 iodide added and the solutions titrated with sodium thiosulphate 
 which was tenth normal. 
 

 n. 
 
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9 
 
 ,^xperi)Tiental • 
 
 A decision was made after various experiments to use as a 
 unit a sample of approxiraately •5/of a gram of Paris Green* 
 
 This Wos dissolved in concentrated ammonium hydroxide dnd the 
 copper precipitated as the sulphide with hydrogen sulphide. The 
 solution was found to be very difficult to filter, hut at length 
 was accomplished hy filtering under suction and keeping the 
 funnel well filled and covered. The copper sulphide then was 
 taken into solution with nitric acid and the copper determined 
 in the usual manner with sodium thiosulphate. The results of 
 the work on the copper were as follows: 
 
 Sample weight 
 
 Thiosulphate used 
 
 Ber cent vopper 
 
 .5326 
 
 20.25 c*c. 
 
 24.29 fo 
 
 .5035 
 
 19.05 c.c. 
 
 24.17 fo 
 
 .5902 
 
 22.60 c.c. 
 
 24.47 f 
 
 .5090 
 
 19.20 c.c. 
 
 24.10 f 
 
 .5501 
 
 20.40 c.c. 
 
 23.69 f 
 
 .5725 
 
 21. 10 c.c* 
 
 23.53 f 
 
 .5011 
 
 18.40 c.c. 
 
 23.46 f 
 
 .5171 
 
 18.50 6.C. 
 
 22.86 f 
 
 .5000 
 
 18 . 45 C.c* 
 
 23.57 °/c 
 
 Factor of thiosulphate = grams of copper per c.c. 
 
10 
 
 Several methods were employed in the work with the arsenic 
 "vi/hen the filtrate, light yellow in color, containing the arsen 
 ic was hoiled, instead of becoming colorless, it turned a rich 
 golden broim which faded on cooling to the original color, 
 attempt was made to oxidize the sulphur in the alkaline solu- 
 tion with hydrogen peroxide or sodium peroxide to a sulphate, 
 and at the same time converting the arsenic entirely to the 
 arsenate. Sodium peroxide was found to be the better oxidizing 
 agent in this case and a 30 gram portion was found necessary 
 so that upon heating the solution became colorless. However, 
 upon making the solution acid with hydrochloric acid a precip- 
 itate started to appear and soon ferric hydroxide came domi 
 followed by arsenic in various stages until it was at length 
 all precipitated as the sulphide. 
 
 To correst this the solutian was made alkaline with sodium 
 hydroxide, and the amount of sodium peroxide then needed to be 
 added in excess, after the solution had become colorless, in 
 ordefi to take care of all the arsenic as well as the sulphur 
 was found to be 20 grams, ^fter strongly acidifying with hydro- 
 chloric acid potassium iodide vras addea and the solutmn tit- 
 rated w$th tenth normal" iodine solution, however the results 
 of this method did not prove constant, and the mechanical work 
 was not smooth. So at length the filtrate was made (l:i) acid 
 with hydrochloric acid to begin with and oxidized with potass- 
 ium chlorate, and the titration then carried out in a similar 
 manner. This proved quite satisfactory. 
 
 ^-^■sodiuni thiosulphate solution, made neutral and an excess of 
 sodium bicarbonate added when the reduced arsenic was titrated 
 v/ith tenth normal 
 

 
 
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11 
 
 Results of Arsenic jD^ terminations. 
 
 Sample weight. 
 
 Xodine 
 
 used 
 
 Arsenio 
 
 .5000 
 
 58.10 
 
 c .c. 
 
 57.51 
 
 
 .5000 
 
 66.50 
 
 c.c* 
 
 65.83 
 
 
 .5000 
 
 63.10 
 
 6 . c . 
 
 62.40 
 
 
 .5000 
 
 57.05 
 
 c.c. 
 
 57.37 
 
 
 .5000 
 
 57.25 
 
 c.c. 
 
 56.68 
 
 
 .5000 
 
 57.40 
 
 © . c . 
 
 56.82 
 
 rif 
 
 T 
 
 .5000 
 
 57.t)5 
 
 c .c» 
 
 57.07 
 
 
 lc.c« iodine solution = .00495 grams arsenious oxide. 
 
 Results of Experimental work on the Ratio of Potassium 
 iodide to Copper in the lodometric Method. 
 
 S-ample 
 
 Acid used 
 
 Kl used 
 
 Thiosulphate 
 
 Salt fonnec 
 
 10 © • c . 
 
 5 c.c. 
 
 0.7513 ^rans 
 
 13 .OOc.c. 
 
 s&ngl e 
 
 10 
 
 5 
 
 n.7504 
 
 13.90 
 
 
 10 
 
 5 
 
 0.7511 
 
 13.85 
 
 
 10 
 
 o 
 
 1.0040 
 
 13.85 
 
 single 
 
 10 
 
 5 
 
 1.0045 
 
 13.85 
 
 
 10 
 
 5 
 
 1.0004 " 
 
 13.85 
 
 
 10 
 
 U 
 
 1.2520 “ 
 
 13.85 
 
 single 
 
 10 
 
 5 
 
 1.2535 
 
 13.80 
 
 
 10 
 
 5 
 
 1.2503 
 
 13.85 
 
 
 10 
 
 5 
 
 1.5270 
 
 13.85 
 
 single 
 
 10 
 
 5 
 
 1.5020 
 
 13.85 
 
 
 10 
 
 5 
 
 1.520 
 
 13.90 
 
 
12 
 
 Sample 
 
 @cid used 
 
 |(l used 
 
 
 Thiosulphate 
 
 ^al t 
 
 10c. c. 
 
 5c.«. 
 
 1.7520 
 
 graans 
 
 13.85c »c « 
 
 single 
 
 10 
 
 5 
 
 1.7539 
 
 II 
 
 13.85 
 
 
 10 
 
 5 
 
 1.7532 
 
 f! 
 
 13.85 
 
 
 10 
 
 5 
 
 2.0012 
 
 II 
 
 13.80 
 
 single 
 
 10 
 
 5 
 
 2.0003 
 
 ft 
 
 13.85 
 
 
 10 
 
 5 
 
 2.0011 
 
 li 
 
 13.85 
 
 
 10 
 
 5 
 
 2.5014 
 
 li 
 
 13.85 
 
 single 
 
 10 
 
 
 2.5012 
 
 M 
 
 13.85 
 
 
 10 
 
 5 
 
 2.5000 
 
 
 13.85 
 
 
 10 
 
 5 
 
 2.7509 
 
 
 13.85 
 
 bigg±e 
 
 10 
 
 5 
 
 2.7520 
 
 -• 
 
 13.85 
 
 
 10 
 
 5 
 
 2.7531 
 
 n 
 
 13.85 
 
 
 10 
 
 5 
 
 3.0018 
 
 ft 
 
 13.85 
 
 single 
 
 Id 
 
 5 
 
 3.2514 
 
 Tt 
 
 13.85 
 
 
 10 
 
 5 
 
 3.2616 
 
 •• 
 
 13.85 
 
 
 10 
 
 5 
 
 3.5021 
 
 •t 
 
 13.85 
 
 o ingle 
 
 10 
 
 5 
 
 3.5016 
 
 
 13.85 
 
 
 10 
 
 5 
 
 3.5024 
 
 
 13.85 
 
 
 10 
 
 5 
 
 3.7504 
 
 
 13.35 
 
 siiigle 
 
 10 
 
 5 
 
 3.7516 
 
 
 13.35 
 
 
 10 
 
 5 
 
 4.0020 
 
 
 13.35 
 
 single 
 
 10 
 
 5 
 
 4.001f? 
 
 
 13.85 
 
 
 10 
 
 5 
 
 4.0024 
 
 tf 
 
 13.85 
 
 
Sample 
 
 Acid used 
 
 13. 
 
 used 
 
 
 Thiosulphate ^iilt 
 
 10 c . c . 
 
 5 c*c • 
 
 4. 500 2 
 
 ,'^raias 
 
 13.85 
 
 $ingle 
 
 10 
 
 5 
 
 4.5014 
 
 n 
 
 13.85 
 
 
 10 
 
 5 
 
 4.5021 
 
 -• 
 
 13.85 
 
 
 10 
 
 5 
 
 5.0008 
 
 
 13.90 
 
 singl e 
 
 10 
 
 5 
 
 5.0014 
 
 
 13.85 
 
 
 10 
 
 5 
 
 5.0021 
 
 tl 
 
 13.85 
 
 
 10 
 
 5 
 
 5.5018 
 
 fl 
 
 13.85 
 
 singl e 
 
 10 
 
 5 
 
 5 . 5024 
 
 tl 
 
 13.85 
 
 
 10 
 
 5 
 
 5.5002 
 
 n 
 
 13.85 
 
 
 10 
 
 5 
 
 G.0026 
 
 If 
 
 13.85 
 
 _ ingl e 
 
 10 
 
 5 
 
 6.0014 
 
 n 
 
 13.85 
 
 
 10 
 
 5 
 
 6.0006 
 
 
 13.85 
 
 
 10 
 
 5 
 
 O.5010 
 
 
 13.85 
 
 single 
 
 10 
 
 5 
 
 6.5021 
 
 •• 
 
 13.85 
 
 
 10 
 
 5 
 
 6.7521 
 
 n 
 
 13.85 
 
 single 
 
 10 
 
 5 
 
 6.7504 
 
 ti 
 
 13.85 
 
 
 10 
 
 5 
 
 657516 
 
 I! 
 
 13.85 
 
 
 10 
 
 5 
 
 7.0007 
 
 
 13.90 
 
 ^ouhiS 
 
 10 
 
 5 
 
 7.0016 
 
 •• 
 
 13.85 
 
 
 10 
 
 5 
 
 7.0021 
 
 n 
 
 13.85 
 
 
 10 
 
 5 
 
 7.5002 
 
 II 
 
 13.85 
 
 aouhle 
 
 10 
 
 5 
 
 7.5004 
 
 
 13.90 
 
 
 10 
 
 5 
 
 7.5021 
 
 ir 
 
 13.85 
 
 
 10 
 
 5 
 
 8.0004 
 
 II 
 
 13.85 
 
 double 
 
 10 
 
 5 
 
 8.5016 
 
 
 13.35 
 
 
> \ 
 
 T'A 
 
 f . '! ► 
 
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14 
 
 onclusion. 
 
 Of the methods employed, the results with copper proved 
 satisfactory, and the last one, that of oxidizing the arsenic 
 solution with potassium chlorate, gave good results also* 
 
 So we present as a nexT metuod for the analysis of Pasis 
 Green the precipitation of the copper as the sulphide followed 
 hy an iodometric titration for the determination of the copper 
 content, and that of oxidizing the arsenic in hydrochloric 
 acid solution folloxFed hy the titrations with thiosulphate 
 and iodine for the determination of the arsenic content* 
 
 Moreover the same amount of Todine is liberated, whether o: 
 not a precipitate is given upon the addition of potassium 
 iodide to copper sulphate solution when titrated X7ith sodium 
 thiosulphate# 
 

 p. tn>70*tfl uSlfw^' ' 
 
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Bibliography. 
 
 1. Roark R.C. J. Ass. Of . A§r. Chemists. Vol 1. 1915rl9l6. 
 
 2. Roark R.C. J. Ass. Of . Agr. Chemists. Vol 3* Page 157» 
 
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