The following is the report of an investigation undertaken for the purpose of collecting further information concerning the influence of solvent upon certain specific properties of solutions. The solvents chosen, including water, represent the lower homologues of the paraffin alcohol series

Fowler, H. E.

Pearce, J. N.

English

University of Northern Iowa

Proceedings of the Iowa Academy of ScienceVolume 24 | Annual Issue Article 721917The Solubility and Heat of Solution of SuccinicAcid in Water and the Paraffin AlcoholsH. E. FowlerState University of IowaJ. N. PearceState University of IowaCopyright © Copyright 1917 by the Iowa Academy of Science, Inc.Follow this and additional works at: https://scholarworks.uni.edu/piasThis Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion inProceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contactscholarworks@uni.edu.Recommended CitationFowler, H. E. and Pearce, J. N. (1917) "The Solubility and Heat of Solution of Succinic Acid in Water and the Paraffin Alcohols,"Proceedings of the Iowa Academy of Science, 24(1), 523-526.Available at: https://scholarworks.uni.edu/pias/vol24/iss1/72'l'HE SOLUBILITY AND HEA'l' OF SOLUTION OF Sl'C-CINIC ACID IN WA'l'ER A;\TD THE PARAFFIX ALCOHOLS. H. E. FOWLER AND J. N. PEARCE The following is the report of an investigation undertaken for the purpose of collecting further information concerning the influence of solvent upon certain specific properties of solu-tions. The -solvents chosen, including water, represent the lower homologues of the paraffin alcohol series. MATERIALS AND APPARATUS. Ordinary 95 per cent ethyl alcohol '"hich had been standinf1 for several months over quicklime was decanted and distilled. The distillate was then allmn'd to stand over anhydrous copper sulphate for several days, thrn decantrd and again distilled. This distillate was next refluxed over metallic calcium for sev-eral hours and again distilled into glass-stoppered bottles, heing protected during the final distillation by a tnhe of phosphorus pentoxide. 'l'he remaining alcohols were of Kahlbaum's "C. P." grade. Except for the preliminary treatment with lime. they were sub-jected to exactly the same treatment as 'ms the ethyl alcohol. In every distillation a Glinsky frnctionating· .-;till-head was used and only the constant-boiling micMle fraction was collected for use. The boiling points of the fractions taken were. Methyl Alcohol ......... . 64°.5-64°.7 at 750.6 mm. Ethyl Alcohol .......... . 77.7 747.2 n-Propyl Alcohol ......... . 96.0- 96.2 743.1 n-Butyl Alcohol .......... . 115. -115.2 745.6 iso-Butyl Alcohol ......... . 105.9-106. 733.1 ter-Butyl Alcohol ......... . 81.2- 81.5 741.7 Succinic Acid.-A high grade of the "C. P." acid was further purified by the rapid cooling of a hot saturated aqueous solu-tion. The fine white crystals 'rere filtered on a Hirsch funnel, sucketl dn:, then allovved to dry on a porous plate and finally allowed to stand over phosphorus pentoxide in a desiccator for at least three weeks before being used. 1Fowler and Pearce: The Solubility and Heat of Solution of Succinic Acid in Water andPublished by UNI ScholarWorks, 1917• 524 IOWA ACADEMY OF SCIENCE Vor.. XXIV, 1917 Benzoic A._cid.-Kahlbaum's "C. P." acid ivas first fractionally resublimed, then fused and preserved in a desiccator until it was needed. Sodium Hydro.ride Solutions.-The solubility vvas determined by titrating weighed portions of the saturated so1ntions ,vith a standard solution of sodium hydroxide, using phenolphthalein as indicator. For this purpose two aqueous solutions of sodium hydroxide were prepared, approximately .5N and .lOX, re-spectively. A slight excess of solid barium hydroxide was added to each to remove any carbonates present. After being allowed to stand_ for some time they were quickly filtered into ceresin-coatecl stock-bottles., Each of these stock-bottles iVHS connected with the upper end of a certified burette by means of a ceresin-coated glass tnbe, thus forming a single piece of apparatus. The burettes were filled ·bl- suction. Entrance o.f carbon dioxide into the apparatus was prevented by trains of test-tubes con-taining the respective standard solutions. The alkaline solutions were standardized (Morey's l\Iethod') by titrating against weighed portions of benzoic acid, care being taken to insure complete neutrality of the alcohol used. Here as elsewhere in the work only hot redistilled water was used. The saturation apparatus consisted of a large glass test-tube (22x150 mm.) provided with a tight-fitting, one-hole rubber stopper. Into this hole was pressed a metal sleeve through which passed the axle of the stirrer and to which was attached a -stout spiral of heavy platinum wire. The only possible open-ing· into the test-tube was kept effectually sealed by the flange of the axle which rotated upon the metal sleeve. The stirrer was driven at the rate of 1,200 to 1,600 revolutions per minute by means of a small electric motor. The saturation apparatus thus arranged was immersed in the constant temperature hath which was electrically heated and electrically controlled at the desired temperature to within ±0.02°. While preliminary experiments showed that saturation is com-plete in two hours, the time allowed for saturation ·was rarely less than four hours. After saturation the stirrer irns stopped, the crystals allowed to settle and several portions of the clear saturated solution were withdrawn by means of certified 5 cc. pipettes. To prevent the entrance of fine crystals into the 1 Bureau of Standards, Scientific Paper, No. 183, 1912. 2Proceedings of the Iowa Academy of Science, Vol. 24 [1917], No. 1, Art. 72https://scholarworks.uni.edu/pias/vol24/iss1/72SOLUTION OF SUCCINIC ACID IN WATER 525 ·pipettes the tips were protected by small muslin filters. These portions were transferred to tarred glass-stoppered weighing bottles and the weight of the solution was determined. · The samples were then transferred to small Erlenmeyer flasks, boiled water added and then titrated to a faint pink color by means of the standard alkali. In every case the final titration was made with the dilute sodium hydroxide. From the data thus obtained were calculated the solubilities. The heats of solution of succinic acid in the solvents used have been calculated by means of the well-known van't Hoff isochore, QT2-T1 lnC2 - lnC1 = H, T 2 ·Ti where R is the gas constant ( 1.985 cals.). C2 and C1 are the sol-ubilities at the absolute temperatures 'r 2 and T 1 , respectively, and Q is the molar heat of solution produced by dissolving one gram-mole of the acid in one hundred grams of the solvent. By a mathematical rearrangement, 2.3026Xl.985XT,XT, l C, Q = T-T og,., 0 cals. ' l ' Succinic acid is but slightly dissociated in water and practic-ally not at all in the alcohols. This relation will give, therefore, a close ap!IJroximation to the heats of solution of the acid in the solvents under consideration .. The results obtained are given .in the accompanying table. Each solubility value given is the mean of three· or four separate values which do not differ by more than a few hundrrdths of a gram per one hundred grams of solvent. TABLE I. SOLUBILITY OF SUCCINIC Acrn. I In Grams Per 100 I In Moles Per 100 Molar Heat Grams of Solvent I Moles of Solvent of Solution Solvent 25° I 30° I 35° 25° I ao0 35° Qi I Q• I Water -----------------8,368 10.295 12.821 1.277 1.571 1.966 7442.5 8142.G Methyl Alcohol -------- 20.460 23.076 26.260 5.502 6.269 7.125 4320.4 4796.9 Ethyl Alcoho1 ---------9.996 11.49'2 :~.18~ 3.899 4.483 5.143 5230.7 5101.0 .,_Propyl --------------4.806 5.665 6.664 2.445 2.882 3.391 5905.4 6027.4 "-Butyl --------------3.179 3.817 4.464 1.995 2.396 2.801 6572.7 5804.4 tert-Butyl ---· ------8.504 9.687 10.949 5.336 6.079 6.871 4680.0 4542.1 Tso-Butyl ----- ------2.532 3.062 3.646 1.589 1.921 2.288 6825.7 6478. 7 lso-!\myl ----- -------· 2.146 2.570 3.133 1.601 1.918 2.338 6474.3 7352.0 3Fowler and Pearce: The Solubility and Heat of Solution of Succinic Acid in Water andPublished by UNI ScholarWorks, 1917526 IOWA ACADEMY OF SCIENCE VoL. XXIV, 1917 Q1 and Q2 represent the molar heats of solution calculated for the intervals (25°-30°) and (30°-35°), respectively. SUMMARY. As might he expected, the solubility of succinic acid increases with rise in temperature in all of the solvents studied. Consid-ering the alcohols alone, the solubility at all temperatures is greatest in the methyl alcohol and decreases rapidly with the in-crease in the molecular weight of the alcohol. Methyl, ethyl, n-propyl and n-butyl alcohols have the simple molecular chain structure. n-Butyl (CII,pH2 CH2CH20H), iso-butyl ( (CH3 ), CHCH20H) and tert-butyl) ( (CH0 )aCOH) are isomeric com-pounds whose molecular structures differ simply in the grouping of the atoms within the molecules. 'l'he effed of these structural differences upon the solubility of succinic acid is to be seen from the table, the solubility being greatest in the tertiary-butyl and least in the iRo-butyl alcohol. The effect of solvent upon the heat of solution is apparently just the reverse of that upon the solubility. For the normal alcohols the heat of solution increases as the molecular weight of the alcohol increases. fokewise, for the isomeric butyl alcohols the heat of sol ntion is greateRt in the iso-butyl and least in the tertiary-lmtyl alcohol. For the temperature intervals studied the heat of solution shows a decided increase with rise in temperature for solutions in water, methyl alcohol and iso-amyl alcohol. 'rhe reverse is equally true for solutions in iso-lrnt.vl alcohol. For the other alcohols the heat of solution may be considered as practically independent of the temperature. Obviously, the heat of solution of a given substance is a specific property of the solvent. These deductions are based eritire1y upon the assumption of the validity of the van 't Hoff isochore when applieLl to solubility methods. Hints as to interesting relations between the solubility of the solute and the surface tension, compressibility and the association of the solvent have been observed. Before any generalizations can be made regarding these relations the work will have to be extended to higher alcohols and these we do not have. P1iYs10Ar, CHEMISTRY L.\BORATORY, THE STATE UNIVERSITY OF IowA. 4Proceedings of the Iowa Academy of Science, Vol. 24 [1917], No. 1, Art. 72https://scholarworks.uni.edu/pias/vol24/iss1/72

The Solubility and Heat of Solution of Succinic Acid in Water and the Paraffin Alcohols

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The Solubility and Heat of Solution of Succinic Acid in Water and the Paraffin Alcohols

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