Aug., 1916
*THE JOC'R-li.4L O F I Y D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
701
ing effect of t h e soaps o n t h e fibers by making tensile strength determinations. S U R F A C E TExsIox-In most of t h e theories which have been brought forth t o explain t h e detergent value of soap, surface tension has played a n important part. I n order t o study the relation between surface FOREST P R O D U C T S L.4BORATORY .MADISOX, WISCONSIN tension and concentration, a number of experiments were made b y means of t h e Traube stalagmometer. SOME STUDlES OF SOAP SOLUTIONS Tt7hile the Traube stalagmometer method for surface By VICTOR LENHER A X D MARYV R BUELL tension determinations possesses certain objections, Received April 3, 1916 these errors are of minor rather t h a n major character. The chemical analysis of a soap shows only t h e conIt was found t o suffice in this work. inasmuch as the stituents of which it is composed. T h e results indiresults are comparative. cate t h e content of water, f a t t y acid as soap, unil bulb was blown in t h e stalagmometer so t h a t j saponifiable matter, alkali (combined or free), glyccc. would be t h e quantity delivered, and a device used erin, salt, filler, etc. S o satisfactory method has whereby t h e pressure could b e regulated. T h e whole been proposed for the determination of t h e real value was surrounded b y a water b a t h and t h e outlet' alof a soap, namely, its cleansing power. From t h e lowed t h e drops t o form in t h e air or in a given liquid. timk of Chevreul, one of the first t o s t u d y soap, t o I n t h e measurements made b y this method, t h e numt h e present d a y , considerable literature has accumulaber of drops were counted and t h e time taken when ted on t h e cleansing power of soap. Some of t h e work a definite volume of liquid was allowed t o flow out is experimental, and some is purely speculative, b u t through t h e pipette. with all t h e thought and energy which has been exSodium oleate solutions were prepared from pure pended on this subject i t must be confessed t h a t sodium hydroxide and very pure oleic acid. When we do not possess sufficient d a t a t o explain satisfacsoap solutions are made t o form drops under the surtorily t h e phenomena ordinarily exhibited b y soap face of a n oil or of a liquid immiscible with water, solutions, nor can t h e chemist tell t h e laundry how t h e nufnber of drops formed is much greater t h a n when much soap is required t o remove a definite amount of a n equal volume of water is made t o form drops under dirt or wash a given weight of soiled clothing. similar conditions, t h a t is, t h e surface tension beVarious phases of t h e question as t o how soap tween oil and water is much greater t h a n the surface acts as a detergent have been studied a t different tension between oil and soap solution, or, the surface times. These studies are well summarized b y Bancroft tension is inversely proportional t o t h e number of in his papers on ernulslfication, now running in t h e drops formed. The relation between concentration Journal oj' Physical Chemistry. of soap solutions and their surface tensions toward T h e various methods which have been suggested some liquids immiscible with water is shown in t h e from time t o time for t h e evaluation of soaps, have accompanying curves. I n all cases t h e temperature depended largely on t h e use for which t h e soap is inwas controlled a t 2 j '. tended. Hillyer' divides soaps into two classes: T h e first point on each of t h e curves is not as accurate those used with cold or lukewarm water, such as as t h e others because a t t h e N/IO concentration toilet soaps; and those used with boiling water, as hydrolysis is fairly rapid. The significance of the laundry soaps. His method for determining t h e de- points is t h a t they show the general direction of t h e tergent value of soap is by t h e Traube stalagmometer curves. The error of t h e observations is considered method for determining t h e surface tension of a soap t o be approximately 0 . j per cent. Theoretically, solution against a kerosene which he arbitrarily t h e point of minimum surface tension should be a t adopted as a standard. The number of drops formed t h e point a t which t h e maximum number of drops is in a given length of time is regarded as a measure formed. I n all of t h e cases investigated, with the of t h e amount of soap in solution, t h e emulsifying single exception of t h e experiment with air, t h e surpower of t h e soap, and its cleansing power. The numface tension was lower with the concentrated solutions ber of drops is referred t o a curve obtained b y running t h a n with t h e dilute solutions, and t h e general direcstandard solutions of neutral sodium palmitate through tion of t h e curves is t h e same. standard kerosene and t h e relative efficiency of t h e I t has been observed t h a t t h e surface tensions soap is t h u s approximated. I n testing soaps intended of sodium oleate solutions toward air are increased for use with hot water, t h e whole of t h e apparatus is surrounded b y a water b a t h which is kept a t t h e de- with t h e dilution. The actual surface tensions of various concentrations of sodium oleate solution sired temperature. toward air were found b y t h e Traube stalagmometer Luksch2 attempted t o determine t h e efficiency of a soap b y coloring pieces of chiffon of different method t o be a t z j" as follows, expressed in dynes sizes and washing t h e m under t h e same conditions per centimeter: h7/S0 X/10 N/20 N/40 N/160 N / 3 2 0 N / 6 4 0 N/1280 in a washing machine. T h e results varied I O per cent, 2 8 20 26 21 25 33 24 17 24 77 25.55 41 2 8 24 91 b u t were sufficiently accurate t o show t h e difference By t h e same method water showed 7 1 . 7 8 toward between different soaps, H e also studied t h e weakenair. It is interesting t o note t h a t with N I I O t o W 3 2 0 1 J A m Chem. S a c , 25, 1256 sodium oleate there is such a small variation in t h e 2 Sezfensiedeu-Ztg , 40, 413, 444.
T h e plant would pay j . j per cent on a n investment of Szjo.ooo without t h e chips and 1 1 . j per cent assuming the chips t o be worth $ 1 . 0 0per t o n for pulp, which is a low estimate since the material would be in condition for immediate pulping.
702
T H E J O U R N A L O F I N D C S T R I A L AAVD E S G 1 4 E E R I A V G C H E M I S T R Y
surface tension, especially when t h e surface tension is so different from t h a t of mater. The solutions in this range of concentration are the ones which foam so well. When a dilution of -V/640 is attained t h e solutions commence t o t a k e on a milky appearance. T h e fact t h a t t h e foaming is so much more profuse between lV/80 and -Y,’320 affords evidence t o the view t h a t in these concentrations we have t h e soap acting as an emulsifier t o produce t h e foam which is a n ”emulsion of air in soap solution.” While the above obserxTations were taken a t 2 j 0 , a study was made a t temperatures of 20, 2 2 . 24 and 2 j ’, and it was found t h a t within this range of temperature t h e surface tension measurements if plotted as a curve form a straight line, showing t h a t t h e rate of flow is directly proportional t o the temperature. E B I U L S I F Y I K G .4CTIOI\’ O F S O A P
Following the lines of our modern methods of preparing emulsions, t h e emulsifying pon-er of soap was
studied. Emulsions of kerosene and mater were made b y shaking kerosene with a n excess of soap solution in a wide-mouthed, glass-stoppered bottle. After t h e mixtures had stood for a few minutes, t h e excess of soap solution separated out a t t h e bottom of t h e bottle, leaving all of t h e kerosene emulsified in t h e upper layer. These emulsions remained permanent for months. If insufficient soap is present when one attempts t o make a n emulsification of this character. either no emulsification or only partial emulsification takes place. I n order t o study this emulsifying action of the soap with water and immiscible liquids, it is noted t h a t , as with other emulsions, simply a uniform shaking, such as given b y a shaking machine, is insufficient. A shaking machine, even when running a t high speed, gives unsatisfactory results. I n fact, a shaking machine does not give as satisfactory results as does the jerky double motion given by hand. The ap-
\‘ol
8, S O .8
paratus found t o be best adapted for the purpose was a thin stirring paddle made of German sill-er in n-hich a large number of holes were c u t . T h e , paddle was electric motor-driven and t h e jar in which it was revolved was immersed in a. constant temperature bath. Vhenever possible, equal volumes of water and immiscible liquid were used a n d t h e amounts of soap varied. I n the first experiments. t h e object 17-as t o ascertain the minimum quantity of soap which would act as a n emulsifier under definite conditions. An emulsion was considered satisfactory if there was no visible separation of either constituent a t the end of j min.; the time of stirring being j min. This standard is not so arbitrary as it might seem a t first sight, because in most cases if t h e emulsion separates This is a t all. it does so in the first half-minute. especially true of the emulsions produced a t the lower temperatures. A test of the accuracy of t h e method showed t h a t a difference of 0 . I cc. S 20 sodium
oleate solution, corresponding t o o . o o r j g., could be readily detected. I n the results given, t h e accuracy has not been worked out t o such a high degree, b u t is approximately 0 . j cc. N / z o sodium oleate, or, 0 . 0 0 7 j g. The experiments were conducted a t 20’ and t h e water used was highly purified. SODIUM OLEATE X E C E S S A R Y FOR
SCBSTANCE
WATER
EMULSIFICATION
cc.
Grams
50 50 cc. Carbon 50 50 cc. C h l o r o f o r m . . . . . . . . . . . . . . . . . 50 50 cc. Benzol.. . . . . . . . . . . . . . . . . . . . 5 0 2 . 5 g. Vaseline.. . . . . . . . . . . . . . . . . . . 50
0.6331
............... Tetrachloride. . . . . . . .
50 cc. T u r p e n t i n e . .
0.1140 0.7824
0.9804 I , 5200
It is obvious t h a t entirely different amounts ’of soap are necessary t o emulsify under the same conditions t h e same volume of different substances which are immiscible wich water. The experiment with vaseline can hardly be compared with t h e others, nor is its accuracy s o great on account of t h e physical condition of the vaseline, b u t is introduced simply t o show its behavior under these conditions.
Aug., 1916
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
EFFECT OF CONCENTRATION ON EMULSIFICATIOK
The effect of the relative amount of water present in emulsions with turpentine was observed. 20 SODIUM TOTAL
TURPENTINEW A T E R cc. 25 25
cc. 0 25 50
25
NECESSARY OF cc. 30 18 8
WATER
Cc. 30 43 58
I t follows from these results t h a t weak solutions of sodium oleate are more economical in t h e emulsification of turpentine with water t h a n t h e more concentrated solutions. I t is, therefore, apparent t h a t t h e volume of water in which a given amount of soap is dissolved is an important factor in its detergent effect. EFFECTOF TEMPERATURE O N EMULSIFICATION WATER cc. 50 50
TEMPERATURE SUBSTANCE 200 500 20 100
c.
50 50 50 50
cc. cc. cc. cc.
Chloroform Chloroform Olive Oil Olive Oil
50 50
SODIUM OLEATE NECESSARY Gram 0.7828 0.4636 0.6384 0.3040
I t is evident from these observations t h a t a definite amount of sodium oleate will emulsify more of these materials a t high temperatures t h a n a t low temperatures. The emulsions produced are, however, not so stable a t high temperatures as t h e low temperature emulsions. T h e emulsions were, however, permanent for j min. in all cases. For this kind of a study no objection can be raised t o emulsification of this character, inasmuch as in t h e actual process of washing, as soon as t h e emulsion is formed, it is washed away. I t is in general true t h a t sodium oleate solutions wash more efficiently a t high temperatures t h a n a t low. Soaps which are relatively high in oleic acid content are often spoken of as cold water soaps. F r o m this it might be inferred t h a t they wash better in cold water t h a n in hot. This is not t h e case. I t is true t h a t they wash better in cold water t h a n t h e stearate or palmitate soaps, which have only a slighi detergent action in cold water. I n general, t h e oleates wash better in hot water t h a n in cold. E F F E C T O F A G E OK S O A P S O L U T I O N
Strong solutions of sodium oleate decompose on standing with t h e formation of a precipitate which in chemical composition is a n acid soap. This precipit a t e is relatively insoluble and cannot be entirely brought back into solution b y boiling. Experiments were made t o find t h e relative emulsifying power of fresh N / I O sodium oleate solutions, and of N11o solutions in which this precipitate had formed. The solutions were thoroughly shaken in order t o insure t h e precipitate being uniformly suspended through t h e solution. WATERADDED
TO
MAKE U P TO
SCBSTAKCE Cc. 5 0 cc. C h l o r o f o r m . . . . . , . . 5 0 50 cc. Chloroform.. . . , , , , 50 50 cc. Chloroform. . , . , . , 50
AGE Fresh 3 mo 4I/z mo.
ently as well as water in which the soap has been freshly dissolved. COMPARATIVE
EMULSIFYING
SODIUM OLEATE NECESSARY Gram 0,7828 0.7904 0,7965
From these experiments i t is evident t h a t t h e emulsifying power of sodium oleate solutions is impaired only very slightly by t h e hydrolysis. and 'a soap solution which has stood for a long time washes sppar-
POWERS
OF
THE
SODITM
SOAPS W H E K U S E D HOT
SODIUM
NECESSARY Gram 0.4560 0.2736 0.1216
703
A comparison of t h e emulsifying powers of pure sodium oleate, stearate and palmitate has been made. N/20 solutions of t h e three soaps were prepared from t h e pure f a t t y acids and pure sodium hydroxide. T h e solutions of t h e stearate and palmitate were prepared hot. Both the stearate and palmitate solutions solidify t o a jelly on cooling. I t is obvious t h a t when a sufficient concentration is necessary t o emulsify a n immiscible liquid with water, it is necessary t h a t these soaps be used a t a high temperature. Such liquids as benzol. carbon tetrachloride and chloroform as were used a t lower temperatures were not serviceable a t 100'. Highly inflammable liquids could not be used in our apparatus; hence olive oil was selected as t h e most satisfactory liquid for t h e purpose. The end-points are not as definite a t high temperatures as a t z j '. The oil was well emulsified b y very small quantities of soap, b u t a considerable excess of soap is necessary t o render the emulsions permanent for j min. OLIVE
OIL
W A T E R TO MAKE U P TO
25 25
Cc. 25 25 25
TEMPERATURE Cc. 100: C. 25 100 1000
-
REOUIRED FOR EMULSIFICATION 0.1672 g. Sodium Oleate 0.1390 g. Sodium P a l m i t a t e 0 2250 g. Sodium S t e a r a t e
I n this comparison it appears t h a t a t 100' sodium palmitate emulsifies olive oil more efficiently t h a n t h e oleate or t h e stearate. These d a t a are very suggestive as t o t h e relative detergent values of t h e three soaps a t the boiling temperature, b u t more experiments should be made along these lines with various substances before it is possible t o generalize. SUSPEKSIONS
I n studying t h e action of soap solutions with SUSpended matter. such as ferric oxide and manganese dioxide. concentrations of sodium oleate from .VI20 t o A V / ~ 2 8 0were used. 2 5 0 cc. of t h e sodium oleate solutions were shaken u p with t h e sifted minerals and allowed t o stand from j days t o 3 weeks. T h e results with t h e two minerals were of t h e same order, and though it was impossible t o make accurate quantitative measurements, it was noted t h a t t h e maximum suspension invariably occurred with about - V i 3 20 solution. Further studies on soap solutions are in progress in this laboratory. UNIVERSITY OF
WISCONSIN,
MADISON
VANILLA EXTRACT By J. R. DEANA N D J. 0. SCHLOTTERBECK Received January 3 , 1916
( C o n c l u d e d f r o m our previous i s s u e ) SECOND-GRADE EXTRACTS
The conclusion reached in regard t o the use of alkali was entirely in regard t o a first-class extract where t h e aroma of t h e extract is of t h e greatest importance. I t is often desirable, however, t o prepare second-
