The ANALYTICAL USES of ETHANOL* G. W. FERNER
AND
M. G. MELLON
Purdue University, Lafayette, Indiana
I
N VARIOUS procedures in analytical chemistry ethyl alcohol has been used for many years. Although water is the analyst's most useful solvent, ethanol seems to deserve considerationfor second choice because of its desirable physical and chemical properties. Its boiling point of 7S°C. and specific gravity of 0.78506 (25") make it preferable to water for some purposes. The substitution of an ethyl group for one hydrogen in water gives a compound the chemical nature of which is changed sufficiently from that of water to make it analytically useful where water is unsatisfactory; yet the change is small enough that the two liquids are miscible in all proportions, which is a fact of distinct analytical significance. Although the development of analytical uses for ethanol probably has an interesting history, time and energy have not been available to trace either this development or to locate all current applications of the compound in this field of chemistry. Such uses are sufliciently important and varied, however, that a summarization of them became desirable before beginning certain investigations in this laboratory. The present paper represents the result of an attempt to classify as many different analytical applications of ethanol as could be found, without expending too much time and &ort, and to give examples, with - typical .. references, to these uses. One encounters in a search for such information an instance where the usual indexes for chemical literature are of little value, since they rarely give any indication of the fact that alcohol is used &-an an&tical method. One must resort largely to searching page by page the publications where such facts may possibly be found. In the oresent case a search was made in various sources, as indicated in the bibliography. Chiefly works of reference were examined, including certain standard or official methods. It is obvious that no general search of all periodical literature could be made in anv reasonable l e " n d of time in order to locate the incidental analytical uses of ethanol. In giving citations for the different examples of uses only one source is mentioned in most cases, even though the method may be found in several publications or in several places in the same publication. In general. it seemed desirable when possible to refer to an official publication, such as that of the Association of Official Agricultural Chemists. Applications were sought not only in the generally recognized divisions of quantitative analysis but also in such closely related fields as chemical microscopy and metallography. There were a few instances in which the reasons for
using alcohol were not entirely evident. Others may well disagree with the authors' classification in such cases. Also there may be an occasional instance in which the application mentioned has been superseded by some improvement suggested since the time of publication of the references examined, as no attempt was made to check all the uses with the latest information available in the periodical literature, in new editions of works of reference, or in the hands of committees, such as that for the revision of the Pharmacopceia of the United States. In the following outline, in order to indicate where a given application may be found, there is included in each case the number (in italics) of the reference in the bibliography and the page of the reference on which the use is mentioned. Ounmm A . Prcpamtion of Materials for Analytical Work. 1. Analytical devices a. Cleaning and drying liquid for apparatus Washing down condenser--(2). 393 6. Crucibles Manroe--washing (N&)rPtCls(l5). 87 c. Collodion ultra-filter As solvent for negative mtton+2). 184; (151, 424 d. Alcohol flame Source of "sulfur-free" heat417), 380 e. Levels Liquid for levels in halane cases j. Thermometers Liquid to fill column-(20). 254 .
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* Presented November 17, 1932, before the Chemistry Division of the Indiana Academy of Science. 243
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Reagents
a. Medium for purification (preparation) COn-free NaOH-323). 480; certain indicators(I0). 134; (12), 67; potassium ethyl dithiacarbonate+3), 11, 394: litmus--13). . .. 11.395: . . ouabain-(19). . .. 479 6. Medium for determination of specific gravity
;:E:
$$another liquid Water-@), 284; (19), 102; chloroform-(9), 200; (161, I, 131 c. Liquid standard for refractive index Alcohol one member of a series(3). 11. 385 d. Without water present)
aFgsEth
Indicators -Those not readily soluble in water-(4), 91; (lo), 133; (19), 493; methyl orange (25), 334; o-chromT-(25). 494; turmmi+(3), 11, 397; (5), 500; (25). 134; (26). bV. others a"'. Standard solutions Aldehyde ammonia-(25). 401; benzaldehyde(25), 413; citral+Z), 353; (9), 461; (25), 414; furfural-(9). 77; (25), 421; salicylic acid42). 387; vaniUin-(25). 413. bY'. Ordinary reagents Acetylacetone--(2%). 245; alizarin425). 139; alkanet+2), 318; (5), 200; aniline sulfate-
a ' . -
(19), 486; a-benzildioxime-(lo), 316; curcumin-(lo), 404; (24), 11; digitonin42). 295; dimethylglyoxime-(23), 135; diphenylcarbazide--(5), 500; gelatin and hematin-(2), 75; morin-(h), 500; nitroso-dimethylanilinc (25), 164; oleic acid--(25), 270; oxalic acid(25), 140; phenylhydrazine-(19). 249, 260; m-phenylenediamine-(2), 354; picric acid( I ); quinalizarin-(lO), 403; potassium ricinate--(25). 143; resorcinol-(25), 396; tannic acid-(9). 581; (19). 493; u r e a s d 2 5 ) , 510, 541: general--(3), 11, 36 b'. Inorganic a'. Acids HCl-esterification-(9). 287; etching-(11). 64; ruthenium chloride-(lo), 291; separation of lithium---(Z3), 69; standard solution--(18), 266; (26); water in absolute alcohol-(25), 334 HClO-wash K C I O r ( 7 ) . 68 HNO-tching-(Il), 63 HzSOa+tching-(11). 68 b". Bases NHs (test solution)-(19). 486 NaOH (sapon5catiou)-nicotin~2), 66; (9). 100; titer test-(2). 285; flour-(2), 228; etching -4111. 68 KOH (saponification)-tristearin-(2). 298; peanut oil-(2), 296; (9), 250; creosote carbonate(19), 120; unsaponifiable residue(2). 295; (9), 261; (191, 463 Standard solutions: acetyl value-(2), 293; menthol-(9), 465; saponification n n m b e r s ( 2 ) . 289; (9). 241; (Id), I. 388; (19). 457; soil acidity-(18). 266
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c". Salt-
Os)1--(19), 489; S n C G ( 1 0 ) . 531; etching mix-
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d". Elements Iodine ( l l ) , 66; (14). I. 405; (151, 411 3. Sample a. Prepaxation a'. Preservation Viscera-(29) b'. Cleanine eta^-(11). 61 6'. Drying Meat-(1), IX, 280; (2). 237; m e t a l e l l ) , 65 d'. Grinding Silicate rocks under alcohol-(lo), 673 e'. Reaystallizatiou Organic a c e t a t e s ( 2 ) . 295; arachidic acid-(9). 251; eeneral-(3). 11. 346 b. Solution a'. As a selective solvent (single or multiple extractionconcentration varying from absolute ethanol to dilute aqueous solutions) a'. Alcohol alone Food analysis, various constituents(2). 132. 136, 140,205,225,252,317,327,333,334,335,347,362; (9). 440: (13). 424: drue analvsis-(19). 139-150. --- -~ technical analysid(2), rb3.293; ( 243; i) 247,, 277, 278, 331, 459, 475; (13), 521; (16), 11, 601: (23). 377; (25). 475 b". Alcoholic solution of a reagent Rosin-(9). 357; soluble coloring matter-(9). 391; oil-soluble dyes-(2). 140; (9), 392; extra*
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tion of rubber--(9), 482; fat-(2). 198, 231, 262. 322; (13). 193; capsicum-(2). 359 b'. As a complete solvent a". Direct solution a"'. As a qualitative test of solubility Castor oil-(9), 263; resins--(16), 11, 597; essential oils--(19); many U. S. P. tests of identity and purity, such as CaCI&H*+(19), 263, and v a n i l l i n j l 4 ) , I, 370; (19). 420: various compounds(1); (21) 6"'. For other qualitative tests Casein-(19). 474; CHsOH-(2). 372; turm e r i c ( 2 ) , 152; turpentine-(16). 11, 588; vanilla resins (2). 351; Ti-(Zl), IV, 447; U-(21). V, 1144; general-(1). I. 257; (3). I I , 7 6"'. For quantitative determinations (gravimetrie, titrametric, electrolytic, or colorimetric) Acetylsalicylic acid-(2). 388; acid n u m b e r s (9), 242, 328; (19). 427; aldehydes (2), 353; (9), 460; arachidic add-(9). 251; alkaloids(2), 383, 390. 404; benzoic acid (2). 129; (lo), 142; cincophen-(19), 110; citral-(2). 354; colors-(2). 162, 374; d y e s ( l ) , VI, 16; essential ails-(19); ester number-(Ig), 437; . free fatty acid-(9). 270; Hehner number-(2). 289; (9), 243; fatty a c i d s ( 2 ) . 292; nitrogen - ( l o ) . 640; phenolphthalein-(2), 401; Paienske number-(2). 291; salicylic acid-(19), 49; spirit of camphor-(19), 351; s o a p 4 2 ) . 65; s u g a r s @ ) , 118. 322; tinctures--(19), 126, 129, 135; tolu-(19), 406; various determinationdzl). 6". Sa~oniiication Paraffin-(9), 419; Reichert-Meissl number-(a), 290; titer test-(g), 246 c. Completion of preliminary reactions a'. Reduction Manganates and permanganates(2). 109; (10). 414, 750; (21). V, 968; (23). 550; (25). 168; precipitation of An and Pd by C.H7(21), IV, 17; alkali ruthenates-(21). IV. 53: Os0-(21). IV.
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d. ~ i l u t i o n ' Aldehydes--(2), 370, 371; glycerol-(I), VI, 45; nitroglycerin-(2). 395; spirit of ethyl nitrate--(19). 349; tincture tests-(19). 387406; vanilla e x t r a c t j Z ) , 351; w i n e s ( ? ) , 374 B. Determination of Constituents. 1. Qualitatively a. Reaction of ethanol with unknown A c e t a t e s ( l 9 ) , 440; acetyltannic acid--(19). 15; bor a t e s ( 5 1 , 368; (lo), 607; (19), 440; chromates(5). 452; (21), V, 953 2. Quantitatively a. Separation of constituents a'. By precipitation a'. To obtain desired precipitate a". Oreanic "Alcohol precipitate": f r u i t s ( 2 ) . 212; foods -(I), IX, 262; (2). 232; gelatin-(2), 217; meat e x t r a d s ( l ) , IX, 514; p r o t e i n s ( l ) , VIII, 675; vinegar42). 330; Bellier test(9). 252 b"'. Inorganic Na and K from Li-(Z), 98; (lo), 527; same from Mg&lO). 508; K from Rh and C s ( l 0 ) . 531: KCIOA-(23). 65. 67: Ca from Me-(15). .. 5971 K from ~ a q 3 0 ) ' b'. To free solution of interfering substances Br and I (mineral w a t e r ) j 2 3 ) . 562; pectic acid --(2), 212; salicylic acid-(Z), 125; A1 saltr-(21), V, 86
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