THE SOLUBILITY OF NORMAL BUTYL ALCOHOL IN AQUEOUS SOLUTIONS OF INORGANIC SALTS BY NELSON JOSEPH ANDERSON B. S., Kansas State Agricultural College, 1920 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN CHEMISTRY IN THE GRADUATE SCHOOL OF THE UNIVERSITY OF ILLINOIS 1922 URBANA, ILLINOIS Digitized by the Internet Archive in 2015 https://archive.org/details/solubilityofnormOOande < UNIVERSITY OF ILLINOIS 0. to r i THE GRADUATE SCHOOL -192-2 1 HEREBY RECOMMEND THAI' THE THESIS PREPARED UNDER MY SUPERVISION BY Nelson J* Anderson — ENTITLED THE SOLUBILITY OE NORMAL BUTYL ALCOHOL XL AQUEOUS SOLUTIONS OE INORGANIC-SALTS BE ACCEPTED AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE DEGREE OF Master- of - Science Head of Department In Charge of Thesis Recommendation concurred in* Committee on Final Examination* Required for doctor’s degree but not for master’s table of contents Page 1 INTRODOCTIOh. 1-2 11 EXPERIMENTAL PART ( a)Di scussion of Methods 3-6 Cb)Tests of Methods Chosen 7-8 III DATA AND GRAPHS 8-19 IV DISCUSSION OF DATA ALD RESULTS ( a) Cations 20-21 (h) Anions 2122 (c) Colloids 22 (d) H-ion Concentration 23 V SUMMARY 24 VI BIBLIOGRAPHY 25 ACKNO V/LED GEME1TT The author wishes to express his sincere thanks to Dr .E.K. Carver and Dr . J.H* Reedy for their constant advice and kind supervision of this work „ . , . , , . J THE SOLUBILITY OE NORMAL BUTYL ALCOHOL IN AQUEOUS SOLUTIONS OE INORGANIC SALTS I INTRODUCTION The purpose of this research is to determine the solubility of a non-polar organic compound in qqueous solutions of various concent- rations of inorganic salts. This data, it is hoped, will be useful to make comparisons with facts khown about precipitation of colloids by means of electrolytes , and to make some general conclusions, Thi s work can be rightfully looked upon as a problem in colloidal chemistry because one can select an organic substance ,as gelatin, which will fonn a hydrosol when it is dissolved in water or in certain aqueous solutions of electrolytes. Thus, when one determines the amount of such a substance that will dissolve in a given solution of an electro- lyte, he is measuring the precipitating power of the electrolyte. Since the time of Thomas Graham, a considerable of work has been done by colloid chemists upon the precipitation of colloids by various electrolytes , and plenty of data is available. Asearch thru the literature shows , however, that no data on the theme of this thesis is available. Inasrnuchas it is possible to prepare a solution of a sol which is transparent , it i s suggested that transparent solutions of an organic compound in water or in an aqueous solution may behave like an emulsoid or a suspensoid. To illustrate this point, if one will shake together a solution of NaCl and the proper amount of n-butyl alcohol, he will notice an opalescence in the mixture ,whi ch upon stand- ing for 30 min. will disappear. If the mixture is shaken well again, , - ■ , « < , I . 2 the opalescence will reappear. Thus, one is justified in "believing that the mixturS contains an emulsoid. For this reason, and for the reason that it is easy to find an organic compound which is not an electrolyte, it was decided to use an organic compound for the tests made in this work. EXPERIMENTAL Some method for the quantitative determination of the amount of a chosen organic solute that would dissolve in a given aqueous solution of an inorganic salt was deemed feasible for getting data desired. A few methods of solubility determination were tried with- out success. They follow in the order in which they were tried. Whatever method is used must insure equilibrium in every sol- ubility tewt made. Hence, we chose at the start a device for agitating the liquid under investigating. A 100c. c. wide muoth bottle was fittec. with a rubber stopper thru which a glass stirer could be operated by a small electric motor. The stopper contained a short delivery tube thru which the organic eolufete could be admitted from a burette into the liquid inside the bottle. Ethyl ether was chosen as the organic solute to use in this experiment. A little ether was introduced upon some water contained in the bottle and the stirrer was set in motion. After a little stirring, the motor was stopped, and it was observed whether all of the ether added had dissolved. If not, a little more was added from the burette, and so on, until it was hoped only a single drop of ether would remain in excess. The chief advantage of this method is that the error thru losn of vapor is reduced to a minimum. Its disadvantage is that one cannot determine accurately when the "end pbint" is reached. Altho any excesn of ether added would float on the surface of the water, one could not determine how much ether to add to get even a fairly accurate solubil- ity determination. An attempt to improve the accuracy that could be gotten with this apparatus consisted in the addition of a small amount of an ind- 4 ^■= ■ ^■,-^^-- ■ 10-.- _ .. - . . , , < « . * , - /• 4 icator to the ether. Para-nitroso dimethyl aniline is green and is very soluble in ethyl ether.but only very slightly soluble in water. It pnpTed unsatisfactory. This experiment suggested that a container siich as volumetric flask would be an improvement. Then, one would be able to determine more easily when a single drop of excess ether is added. Such a flask would limit the upper exposed surface of the liquid inside it to the area of the cross section of the neck of the flask. A piece of rubber tubing about 5 in. long wqs used to connect the jet of a glass burette to a short jet made from a piece of glass tubing. This latter jet wa® made quite small so that a liquid flowing thru it from the burette would flow very slowly. This jet was lowered in some water in a 200c. c. volumetric flask until it reached the bottom of the flask. It was hoped that the ether would flow out of th< jet so slowly that it would dissolve in the water before any droplets reached the surface of the water. There would be two advantages in this kind of a scheme. Loss of ether due to evaporation would be small. As soon as droplets began to reach the surface of the liquid in the flask, the "end point" would be attained. A litt-ifc agitation of the liquid by gentle shaking of the flask was thought to be sufficien' This method did not succeed because the rate of miscibility of ether with water or with aqueous solutions of salts is very slow. Also, the droplets of ether instantaneously shot to the surface when first ad- mitted to the water. The large difference in their densities and the low adhesive force between the liquids partly account for the failure of this method. One method which would undoubtedly work wellf\be cause it requires slow work for manipulation. A small excess of an organic < solute could "be shaken with an aqueous solution in a separatory fun-& nel that has a stem with a very small bore. After the mixture is shak- en until equilibrium is reached, the excess of organic solute, being of greater density , would appear at the upper surface of the mixture and an accurate separation could be made. In this way, the determinations could be either gravimetric or volumetric. A small but negligible er- ror would be introduced by the amount of aqueous solution or the elec, trolyte which is dissolved in the excess of the organic solute. One difficulty to overcome, as revealed by the foregoing att- empt s,was to find an organic solute which has physical constants app- roximately equal to the physical constants of water. Such a compound would not introduce appreciable error thru evaporation. Ether was ob- jectionable because of its low boiling point and its volatility. Fur- thermore, a compound which has a high adhesiire force with water and with aqueous was needed; so that, when solubility determinations are be- ing made , equilibrium can be readily attained. A compound that is very soluble is undesirable. Iso-butyl alcohol was selected at first as it fulfils these re quirements ,but w r as later rejected because of the difficulty of purify- ing it. The solubility results obtained with iso-butyl alcohol v r ould not check. The description of a very elaborate method for the purific- ation of higher alcohols is given in an article in the J. A. C. S. , March 1921. pp. 561. The authors suggested that normal butyl alcohol can be very satisfactorily purified by ordinary fractional distillation. Normal butyl alcohol was selected for the solute used in the solubility determinations made in this work. The boiling point of nor- mal butyl alcohol, as given in the article mentioned above, is 117.7 a e- grees C. at 760 mm. pressure. The fraction used for the determinations in this work was that which diatilled over above 116 degrees C. 6 Solubility tests with this grade of alcohol made in pure water and in several salt solutions gave good checks , dhowing the alcohol to be of sufficient purity. 16.85 c.c. of this grade of n-butyl alcohol will dissolve in 180 c.c. of distilled water at 25 degrees C. The method of solubility determination used is as follows; 180-190 c.c. of an aqueous solution under investigation was put in a 200 c. c. volumetri c flask and n-butyl alcohol was admitted from a bur- ette so that the amount added could be read off. The "end point" was reached when a single drop of alcohol in excess floated on top of the mixture in the flask after equilibrium is reached. It was always mana ged so that the total volume of mixture in the flask would be great enough to raise the upper surface into the neck of the flask. This made it possible to determine whenp,drop of excess alcohol appeared. In most cases tried, a few droplets would appear at the surface after a vigorous shaking as soon as the amount of alcohol added was within onehalf of a c.c. of the amount required for saturation. Further shak- ing would usually cause all of these droplets to disappear. It was un necessary , however , to reach the" end point"by the slow process of shak- ing the mixture after each small addition of alcohol until all drop- lets had disappeared. Every solubility test was made in duplicate in two separate volumetric flasks. The first one in eqch determination gave the approximate equilibrium value; the second served to get a more accurate value and to check the first. A glass stirrer was used sometimes to hasten the equilibrium. This stirrer was operated by a small electric motor. It was proved later that the stirrer was un- necessary and that vigorous shaking of the flask for 1 minute was sufficient 7 Several tests were made to prove the accuracy of this method of solubility determination. It was questionable whether equilibrium could be attained in such a short period of agitation as has just bee> described. Two 180 c.c. samples of distilled water were used to test the method. To each enough n-butyl alcohol was added to reach the equilibrium value of 16.85 c.c. fo the alcohol at 25 degrees C. by the method of shaking vigorously for one minute. Then one drop of excess alcohol was added. The flasks were stoppered with glass stop- pers and allowed to stand for three days. During the course of those three days, they were given an occawsiOnal vigorous shaking. At the end of that time they were placed in a thermostat and left until the initial temperature of 25 degrees was attained. The excess drop of alcohol appeared at the surface of the mixture as it was initially just after the one minute shaking. There was no noticeable change in its ifcze. This same procedure was used for samples of N NaCl soln., 2h sodium sulfate soln.,and 0.5JM calcium chloride soln. In every case complete saturation was proved to be attained by the one minute of agitation. To test further the method used for the determinations , two 180 c.c. samples of normal sodium sulfaten soln. wereused. Enough of the alcohol was added to reach the equilibrium value as indicated by the method of vigorous shaking for 1 min. Asingle drop in excess was added to each fo the two flasks. They v/ere securely stoppered, and placed on a shaking machine. They were allowed to shake for 36 hours* removed, and placed in the thermostat to attain the original tenperatu* of 25 degrees, C. That excess drop of alcohol had not di sappearedin either flask. There was no noticeable change in its size in either case. I . • . . 8 These tests were accepted ass proof that the method is satis- factory. Allof the data embodied in this report was obtained at con- stant temperature of 25 degrees C. It is accurate to a tenth of a c.c in every case. All solutions were kept in the thermostat at 25degrees Much time was spent in preparing pure solutions of the variou salts and standardizing them. Chlorides were standardized by the pre- cipitation of AgCl and weighing the precipitates. Sulfates we re stand- ardized by Barium Sulfate precipitation, Cerous nitrate was standard- ized by precipitating with oxalic acid and igniting the oxalate to ceric oxide. Potassium ferricyanide was standardized by precipitating the iron and igniting the residue to ferric oxide. Ill data and curves Plate I contains all of the data of sections 1,2, 3, 4, 5, 6, and 13 of the data sheets. Plate II has represented in its curves the data of sections 1,10, and 11. Plate III has represented in its curves the data of sections 2 and 9. Plate IV contains data of sections 2, 4, and 7. Plate V contains the data of section 8;Plate VI has thS data of section 12. ( Insolubility of n-butyl Alcohol in KC1 Solution Normalitj'- c.c. ofn-butyl per 180 c.c. of aqueous soln.of KC1 . 0.5— - - 13.80 1.0 11.65 1.5 - 9.05 2.0 — — — - — — 7.87 3.0 --- — -- — 5,10 4. 0 ( Sat. ) -- 3.40 (2) Solubility of n-butyl Alcohol in Solution. Normality c.c. of n-butyl per 180 c.c. of aqueous soln. of NaCl. 0.5 — - — - -- 13.0 0 1.0 10.40 2.0 ———— — — —— — -7.00 3.0 — - 4.40 4.0 3.25 5.0 2.13 (3Solubility of n-butyl Alcohol in LiCl Solution. Normality c.c. of n-butyl per 180 c.c. of aqueous soln. of NaCl. 1.0- — - — 12.30 2.0 - - 9.10 2.3---- - 8.00 ( 4) Solubility of n-butyl Alcohol in CaClr, Solution. homality c.c. of n-butyl per 180 c.c. of aqueous soln. of CaClo. 0.5 14.50 1.0 12.40 2.0 10 3.0 --------------- 6.40 4.0 --- 5.12 6.0- — — - 2.84 8.0 1.90 10.0 ------------------------- 1.13 ( 5) Solubility of n-butyl Alcohol in LIgCl 0 soln. formality c.c.. of n-butyl per 180 c.c. of aqueous soln. of MgClg. 0. 5------------ ---------------14. 50 1.0 --------12.90 1. 5-— — ,----- — -----11.40 2.0- — - - — — ----------- 9. 40 3.0 4.0 — .------6.40 6.0 — 4,17 8.0— -------------------3.22 Sat. ■-- — - — -------------- 1. 30 ( 6) Solubility of n-butyl Alcohol in Ce(N0 3 )3 Solution. .Normality c.c. of n-butyl per 180 c.c. of aqueous soln. of 00(1103)3. 1.0 ----------14.60 2.0 -- - — -12.75 3.0 10.40 4.0 -- --------8.55 5. 46 6. 68 ( 7 ) Solubility of n-butyl Alcohol in a Mixture of Equal Parts by Volume of NaCl and CaCl 2 Solutions. formality c.c. of n-butyl per 180 c.c. of aqueous soln. of mixture. 1 . 0 ' 11.50 2 . 0 - 3.0- 4.0- 5.0- 8.10 5. 50 3. 50 2.27 ( 8 ) Solubility of n-butyl Alcohol In Mixtures of CaCl 2 and NaCl Solutions in Which the Cl Ion isKept at a Constant Concentration of I NORMAL but in Which the Cations are Varied in Concentration. Normality c.c. of n-butyl per 180 c.c. of aqueous soln.of mixture. 1/10 N Ca and 9/10 N Na— - — 11.10 2/10 » » " 8/10 " " ----11 ^10 3/10 •' M " 7/10 " --------11.10 4/10 " » » 6/10 " " — «= — -11 . 30 5/10 •' »» M 5/10 " " — -11.50 6/10 " " « 4/10 " M -------11.55 7/10 « " " 3/10 " --------11.75 8/10 » « " 2/10 " »-=- --------12.00 9/10 " .. 1 . 1/10 » «--- --------12.20 0.1 /10 " " "9.9/10 " "--- 0/10 » " " 10/10 » "--- ------ - 10.40 10/10 " " » 0/10 » " — - --------12.40 Solubility of n-butyl Alcohol in Na 2 S0 4 So Normality 0 • 0 . 0 3 1 of aqueous soln. of Na 2 S 04 . 0.5 ----- -------- 12.30 1.0 - 9.00 1.83 - 5.60 (10) Solubility of n-butyl Alcohol in K 2 SO 4 Solution. Normality c.c. of n-butylper 180 c.c. of aqueous soln. of K2SO4 1.0----------------- — - 9. 50 1.30----- - — — - — 8.00 (11) Solubility of n-butyl Alcohol in K 3 Fe(CN)g Solution. .Normality 12 c.c. of n-butyl per 180c. c. of aqueous soln. of K.3Fe( 011)5 1 . 00 - 2 . 00 - 2 * 7 .^ , • uu' • 11.20 -7.65 ■ - 6 . " ■: (12) Solubility of n-butyl Alcohol in Mixtures of NaoS04 and NaCI in which the Na Ion is Kept at a Constant Concentration of I Normal, but the SO4 and Cl Ionic Concentrations are Varied. Normality c.c. of n-butyl per 180c. c. of aqueous soln. of Mixture. 9/10 N Cl and 1/10 N SO 4- • — — — — 10.40 8/10 11 ti 1 " 2/10 11 II — — — — 10.30 7/10 if 11 < " 3/10 11 II — — 10.20 6/10 n 11 1 » 4/10 n II — — — — 10.10 5/10 n 11 1 " 5/10 11 II • — — 9.80 4/10 11 n 1 " 6/10 n II -------- 9.75 3/10 n 11 1 » 7/10 11 II __S.60 2/10 n 11 " 8/10 11 II ---------9.50 1/10 it ti 1 » 9/10 it II - — — ---9.35 0.3/10 n n 1 "9.7/10 11 II — 9.10 0/10 11 it » 10/10 n It — — — - 9.00 10/10 ti n » 0/10 ti II 10.40 (13) Solubility of n-butyl Alcohol in HC1 Solution. Normality c.c. of n-butyl per 180c. c. of aqueous soln. of EC1. 0.50 15.75 1.00 - -16.50 , - ... 0 / i 3 Y- 5 & 7 % f “‘i 1 ^ formality of aaueous solutions . * - . 2 & c . c, of alcohol 16 Solubility of n- butyl in pure water.; PLATE III SOLUBILITY CURVES EOR E-BUTYL ALCOHOL IE AQUEOUS SOLUTIONS OP SALTS HAVING THE SAME CATION BUT DIFFERENT ANIONS. 3 A f ~ 5" “T NORMALITY T % T~ sc al dohol PLATE IV SOLUBILITY CURVES FOR U-EUTYL ALCOHOL BALTS OF TWO PURE IN AQUEOUS SOLUTIONS AND FOR A MIXTURE CONTAINING EQUAL EQUAL VOLUMES OF CONCENTRATIONS AND EACH n- butyl in pure water ^ NORMALITY Normality IV 20 GENERAL DISCUSSION OF DATA AND RESULTS The curves of plate I show that the solubility of n-butyl alcohol is related in some way to the valence of the cation of the salt whose solution is used as the solvent. The alcohol is least sol- uble in the aqueous solutions of salts having monovalent cations, and most soluble in the aqueous solution of the salt having a trivalent cation. A possible explanation is that n-butyl is slightly positive in an aqueous solution of an inorganic salt ; therefore , its solubility is greater in solutions containing bivalent or trivalent cations than in solutions containing monovalent cations. In the case of col- loids , Schulze ’ s Law says: "The coagulatihg power of electrolytes as a rule increases rapidly, wi th the valence of the active ion." The active ion is determined by the nature of the sol. If it is negative, the positive idn is the active one,aad vice versa. If an excess of n-butyl alcohol is added to a givrn quantity of any of these salt solutions , and the mixture is shaken until saturation is reached, one can usually find some of the salt present in the layer of excess alcohol. This indicates that if to an aqueous solution of the alcohol some electrolyte is added, part of the alcohol will be precipitated and the precipitate will be combined with some of the salt. This happens when an electrolyte precipitates a sol jmorSover , the precipitate always has associated with it some of the electrolyte usually an electro-equivalent aifiount of the active ion. Evidence that n-butyl alcohol forms a colloid with an aqueous solution of an inorganic salt and shows properties of a colloid is furnished when some alcohol is shaken with a dilute salt solution • .. .V. - Anopalescence appears, and then disappears within 30 minutes if the mixture is allowed to stand. This opalescence cannot be due to cry- stals of aalt because its disappearance is not accompanied by precip- itation. There is a possible exception to this last statement. Pot- asaium sulfate precipitated out when its concentrated solution was saturated with the alcohol. It is likely that the potassium sulfate solution was supersaturated. It was a saturated solution and the low- ering of the temperature may have supe rsat urate d it. Potassium sulf- ate did not precipitate out from dilute solutions. The opalescence did not occur in concentrated aqueous solutions of salts tried be- cause the amount of alcohol in the solution was insuff i cient ,and also because the salt was associated with most of the water pres©nt,none being left to form a colloid. The salt soluti ons , however , could not bej concentrated enough at 25 degrees C. so that n-butyl alcohol was in- soluble in them. The curves of Plate I show that the position in the electro- motive series of the elements , constituting the cations of the salts, is in no regular manner a determining factor in the solubility of the alcohol. Por instance, Ca stands above Mg in the electromotive series,; but the alcohol is more soluble in concentrations of KgCl 0 ,3 N or higher, than it is in the same concentrations of GaCl2. In concentrat- ions less than 3 N , the solubility is the same in the two solutions. K stands above^in the electromotive series and the solubility of the alcohol in KC1 is greater at any chosen concentration than it is in ITaCl of the same concentration. But, Li is lower in the series than either Ma orK; nevertheless , tha solubility of the alcohol is greater in LiCl solution than in either LaCl or KC1 solutions. The solubility of the alcohol undoubtedly depends upon mol- ecular association. Plate V shows that when a mixture of NaCl and - * > . , « , r CaCl2 solutions are used for the solubility test, the addition of a 2 very small amount of Ca ion greatly increases the solubility of the alcohol. CaClg is outstanding in its power to associate molecules with substances. N- butyl alcohol no doubt forms an association pro- duct with CaCl 2 . Thus more alcohol can be dissolved in a solution containing it. It is probable that this association product is at least as soluble in water as CaCl2 itself. Anhydrous CaCl 2 dissolves in n-butyl alcohol to the extent of 0.124 gm.per 12 c.c. This fact association indicates that molecular/^occurs with CaCl2« Plate VI shows that the presence of a very little Cl ion in the mixturfi of NaCl and l\ T a 2 S 04 increases the solubility of the alcoh^ ol considerably. The increase in solubility with the increase in am- ount of Cl ion present is not , however , as rapid as in the case of the Ca ion just described. Plate VI indicates, nevertheless , that the solubility is dependent upon molecular association in general, and is not limited to the case of CaClo, It shows further that anions have an influence in molecular association similar to that of catiois, In order to find out what influence the H-ion concentration has upon the solubility of the alcohol, the solubility of the alcohol in aqueo&s solutions of HC1 was determined. Plate I shows that when the concentration of the HC1 is I normal, or less, the solubility of the alcohol is less than it is in pure waterjhence ,e. small K-icn concentration does not increase the solubility of the alcohol. There- fore, we cannot attribute the increase of solubility that accompanies the increase of valence o fthe cations to hydrolysis with the conseq • uent formation of H-ions. It has been shown (The Chemistry of Colloids by W.W. Taylor, Chapter IX) that when a sol is precipitated by an electrocute , the L2J amount of the active ion combined with the precipitated coagulate is proportional to the electro- cbemi cal equivalent of the ion. A similar relation may exist in the phenomena occuring in the tests made in this work. But, it is not evident from the data because other influenc » as valence and association interfere 24 V SUMMARY (1) The solubility of normal butyl alcohol in an aqueous solution of an inorganic salt depends upon the valence of the ions of which the salt is composed. (2) In general, the alcohol is most soluble in a given concentration of the salt whose cation has the highest valence, and least soluble in the salt whose anion has the highest valence. (3) The valency rule for colloids that, in general the coagulating powers of electrolytes increase rapidly with the v a lence of the active ion"applies to n-butyl alcohol in aqueous solutions of electrolytes. (4) The solubility of the alcohol does not depend upon the electro- chemical equivalents of the ions of the salt. (5) The greater solubility of n-butyl alcohol in aqueous solutions of salts having cations of high valence is not due to H-ion concentration. (6) The solubility of the alcohol depends upon the property of the salt to form associated products, and is most soluble in the aqueous solution of the salt that most readily forms associated products. , . 25 BIBLIOGRAPHY Frankfurter, J. A. C. S. ,36,1103(1914) Scholes, J.A. C.S, , 33,1309 Bell , J.Phys . Chem. ,0,537 Snell , J.Phys. Chem. ,2,458 Taylor, "TheChemistry of Colloids" , Chap. IX. Chera.Ahs. ,Vol.l5,Part I , 1921 , pp . 965 , 1734 , 2374 , 3921 , 2371,3237. Washburn , "Principles of Physical Chemistry',' pp. 441-445. Brunei, Crenshaw, and Tobin, J. A. C. S. , March, 1921 ,pp. 561-580.