* T H E J O L'RNAL O F I N D C ' 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
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set of experiments ordinary distilled water was used having a conductivity of about 6 X IO-^, The invert sugar was determined b y titration with Fehling's solution which h a d been standardized against chemically pure dextrose. The results of t h e experiments are given in Table I. T h e pressures are expressed in kilograms per square centimeter above atmospheric pressure. PRESSURE Above atmospheric Kg. per sq. cm. 1 1 1
1.25 1.25 1.25 1.25 1.5 1.5 1.5
TABLEI-EXPERIMENTAL RESULTS CONCENTRATION PER CENT INVERSION TEMP. TIME G . Cc. Beet Cane ' C. Hrs. Sugar Water Sugar Sugar I20 50 50 0178 I .33 120 50 50 3.40 10.25 120 50 50 12.38 31.98 123.5 5.97 150 150 8.46 123.5 100 200 123,s 75 50 38.76 50 123.5 200 42.18 .... I 25 25 9 65 127 15.29 2 25 25 54.40 12i 75.72 127 3 25 25 91.02 93,72
An analysis of the results in Table I leads one t o believe t h a t t h e cane sugar solutions hydrolyze more readily t h a n beet sugar, b u t from another series of experiments which we ran we would say t h a t i t depends upon t h e purity of t h e sugar used. Cane sugar is perhaps more likely t o be pure and, therefore, less likely t o contain negative catalyzers. Of course, if beet sugar contains impurities, one might expect it t o contain a catalyzer, b u t such does not seem t o be t h e case, a t a n y r a t e with t h e samples we examined. It will be noticed t h a t b y increasing t h e temperature a n d pressure t h e inversion increases a n d b y lengthening t h e time sufficiently I O O per cent could be produced. From t h e I 23. j runs it seems evident t h a t concentration plays a part a n d within certain limits it might be said t h a t t h e more dilute t h e greater t h e hydrolysis. We also r a n a set of experiments in which t h e t e m perature was 1 2 4 " C. and t h e pressure 1.37j kg. We used cane sugar, beet sugar, and rock candy. T o dissolve t h e sugar, ordinary t a p water which was slightly alkaline, t h e distilled water already mentioned a n d distilled water which h a d been recently boiled, were used. Here we found t h a t in each case where t h e t a p water was used t h a t t h e hydrolysis had been retarded very considerably a n d t h e resulting solution was brown, showing considerable caramelization; this was not shown in a n y of the other runs. The beet sugar showed t h e same amount of inversion as t h e cane ( b o t h of these samples were different from t h e material used in t h e first set of experiments), a n d t h e rock candy showed considerably greater inversion in every case. This would seem t o indicate t h a t t h e purer t h e sugar t h e greater t h e inversion. The inversion is undoubtedly due t o t h e hydrogen ion concentration of t h e solutions a n d me h a d hoped t o make such measurements. Kullgren' states t h a t t h e inversion of a sugar solution may be almost completely accounted for by t h e degree of dissociation of water a n d sugar with t h e rise of temperature. We believe t h a t a concentration of I sugar : j water will give t h e most satisfactory results when a pressure of 1.375 kg. and a temperature of 124' C. is used; t h e time can be adjusted t o suit t h e needs. Since a syrup containing 8 5 sugar : roo water is 1
Z. p h y s i k . Chem., 41, 415.
1'01. 7 . SO. 7
usually needed in preserving a n d t h e amount of invert sugar in t h e syrups on t h e market is about jo per cent t h e n a more dilute solution might be s t a r t e d with, t h e inversion run to 90 per cent or more iE desired a n d t h e necessary sugar t o bring it u p t o t h e proper concentration added later. I t is necessary t o avoid too great concentration when inverting and also too great a temperature and pressure or there will be some caramelization. a thing which, of course, must be avoided. I t is obvious t h a t the manufacturer in making these invert sugar solutions must choose sugar a n d water with considerable care. LABOR.ATORY OF FOODA N D Dnuc ANALYSIS ITNIVERSITY OF h I l C H I G A \ n . A N N ARBoK
REDUCTION OF COPPER OXIDE IN ALCOHOL VAPOR IN REDUCING SUGAR DETERMINATIONS AND COPPER ANALYSIS B y .4. WEDDERBWRN Received January 14. 1915
I n t h e usual gravimetric invert sugar determination, t h e reduced copper is weighed as CunO or after ignition as CuO. In weighing either oxide there is always some doubt as t o t h e accuracy of t h e result. It is difficult t o d r y t h e cuprous oxide with certainty t h a t some oxidation does not occur a n d further t h e oxide is liable t o be contaminated with organic matter, giving a high result. If ignited t o t h e higher oxide, great care is necessary t h a t t h e oxidation be complete a n d t h a t t h e crucible be not held i n t h e reducing flame, t h e action of which would cause a partial reduction. Even if t h e cuprous oxide is heated in a muffle furnace. considerable time a n d care are necessary t o insure a complete oxidation t o CuO. The hygroscopic nature of cupric oxide makes i t difficult t o weigh with accuracy. I n t h e hands of t h e ordinary laboratory assistant I have found a difference of as high as 1 2 mgs. after careful re-ignition of t h e weighed cupric oxide. The ideal method is t o weigh t h e copper in t h e metallic state. I n accurate work t h e metal is obtained b y t h e electrolytic method or by reducing t h e oxide in hydrogen. Both of these methods require considerable manipulation a n d time, also special app a r a t u s not available in most sugar-house laboratories. With t h e purpose of simplifying t h e electrolytic method a n d avoiding t h e use of expensive platinum cathodes, I made some experiments in electrolytically depositing t h e copper directly from alundum crucibles on copper cathodes, with partial success. I found some difficulty in cleaning t h e copper cathodes perfectly, prior t o weighing. Alr. G. L. Spencer' advised t h a t t h e copper could be readily cleaned b y heating t o redness a n d immersing in strong alcohol. This suggestion led t o t h e reduction method described below. T h e cleaning action of t h e alcohol is merely t h e reduction of t h e film of oxide t o metallic copper a n d it interested me t o know t o what extent a precipitate of copper oxide could be reduced by t h e same means. A precipitate of cuprous oxide was collected on an 1
Chief Chemist of the Cuban-American Sugar Company.
July,
101j
T H E J O t ' H S d L O F I A Y D l - S 7 ' K I . l L .1 S D E S G I S E E R I S G C H E M I S T R Y
alunduin crucible, Tvashed with hot water. t h e crucible heated t o redness and immersed in 95 per cent alcohol. T h e reduction was complete. t h e deposit of metallic copper adhering very firmly t o t h e walls of t h e crucible. 9 number of trials with solutions of known strength gave very accurate results, b u t the shock t o t h e crucibles was too great, many of t h e m cracking after being used t w o or three times. T o avoid t h e breakage of crucibles t h e reduction w a s next tried in t h e vapor of alcohol and with entire success. T h e details of t h e method follow. Collect t h e suboxide of copper on a n alundum filtering crucible, using Spencer's filtering funnels with suction. Thoroughly wash with hot water followed b y alcohol. Heat t h e crucible t o redness a sufficient time t o burn off a n y organic matter t h a t m a y accompany t h e copper oxide. Allow t h e crucible t o cool until t h e redness just begins t o disappear and then immerse it in an atmosphere of alcohol vapor as follows: Bend tlic n-ire ends of a small pipe stem or silica covered triangle so as t o form a tripod support for t h e crucible and set t h e tripod on t h e bottom of a 400 cc. beaker, preferably of metal. P u t into the beaker sufficient strong alcohol (denatured alcohol will answer) t o cover t h e b o t t o m t o t h e depth of about I cm. a n d cover t h e beaker with a watch glass. Heat t h e alcohol t o boiling a n d continue heating until t h e \-apors begin t o condense on t h e under side of t h e cover' glass, then place t h e hot crucible on t h e support above t h e alcohol a n d replace t h e cover glass. If t h e crucible is too hot t h e alcohol m a y t a k e fire b u t t h e flame m a y be readily extinguished b y blowing directly on t o p of t h e cover glass, and no h a r m is done. A4110irt h e alcohol t o continue t o boil a moment after putting in t h e crucible, t h e n remove t h e beaker from the source of heat. T h e heat radiated from t h e crucible will prevent a n y further condensation of alcohol on t h e cover glass. T h e crucible should remain in t h e covered beaker until cooled t o a temperature a little above t h a t of t h e alcohol vapor t o prevent oxidation of t h e copper. About 3 or 4 minutes is sufficient. I t m a y t h e n be t a k e n from the beaker a n d t h e cooling be finished in a desiccator. preliminary t o weighing. If t h e crucible is quite cold when t a k e n from t h e beaker it should be moistened with a little pure alcohol a n d this be burned, holding t h e crucible in an upright position. Xfter t h e alcohol burns off t h e crucible is ready for cooling in t h e desiccator. X porcelain Gooch may he used if preferred. T h e reduction t o metallic copper is almost instantaneous and is complete. T h e results are identical with those b y reduction in hydrogen, closely approximating t h e electrolytic method. This method may be used in copper analysis. t h e separations being made in t h e usual way a n d t h e copper collected in a n y form readily burned t o t h e oxide. If in form of copper sulfide t h e precipitate forms in clots a n d is burned t o t h e oxide with difficulty. I t is preferable t o dry t h e sulfide, roast i t gently, a n d then with a glass rod flattened a t one e n d , crush it t o a powder. T h e rod should be wiped off with a piece of ashless filter paper and t h e paper burned
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in t h e crucible. The heating may t h e n he continued t o drive off all sulfur and t h e oxide reduced in alcohol vapor. T H E CVEAS-.iMPKICAN SUGAR COMPASY
CESTKAI,"TINGUAKO," PSKICO, CUBA
THE DETERMINATION OF LINT IN COTTONSEEDMEAL By R . S . B R A C K E T T Received January 7 , 1915
TT'hile a t first sight i t might appear an easy m a t t e r t o determine t h e amount of lint in cottonseed-meal b y purely mechanical means, it has been found impracticable t o do so with any degree of accuracy. T h e following chemical method of estimating t h e lint was worked out and found t o give x-ery satisfactory results: As preliminary t o t h e work i t was first ascertained t h a t alkali a n d acid of I , z j per cent strength, as used for crude fiber' determinations, was practically without action on lint. X sufficient amount of cottonseed was t h e n freed from lint b y first picking a n d finally singeing t h e last. portions carefully t o avoid injury t o t h e seed. T h e seeds were t h e n cut open a n d t h e meats remox-ed completely from t h e hulls. Crude fiber2 was prepared from both the hulls anti t h e meats, b y t h e method above referred t o . T h e crude fiber t h u s prepared was treated, in 0 .z-gram portions side b y side with t h e same weight of lint, on a boiling water b a t h , with z j cc. of a solution of zinc chloride for three minutes, the time required t o dissolve the lint. In this way t h e action of t h e zinc chloride3 solution on t h e crude fiber was determined, a n d t h e necessary correction made in carrying out a determination of lint in ordinary cottonseed-meal. T h e zinc chloride solution was prepared b y dissolving metallic zinc in concentrated hydrochloric acid, concentrating until t h e solution solidified on cooling, a n d t h e n adding twice t h e weight of 40 per cent hydrochloric acid. On treating t h e crude fiber and lint with t h e zinc solution, t h e contents of t h e beakers x e r e stirred vigorously during t h e three minutes nece t o dissolve t h e lint, a n d filtered hot through weighed porcelain Gooch crucibles with asbestos m a t s ; t h e residues in t h e case of t h e fibers were washed with z j cc. of t h e zinc solution. then with water a n d finally with a little 9j per cent alcohol dried and weighed. E X . ~ M P L E - - ~ ~treating 0 . 2-gm. portions of ( ( i ) crude fiber from hulls. ( b ) crude fiber from meats. and ( c ) "crude fiber" from a cottonseecl-meal! ivith z j cc. of a zinc chloride solution for three minutes, the amount dissolyed was as folloivs: ( a ) 0 . 0 6 8 ; g . . ( b ) 0 . 0 6 ; 8 g. a n d (c) 0 . 1000 g . T h e correction was. therefore, 0 . 0 6 8 2 5 gram. Hence t h e amounL of lint in t h e "crude fiber" from t h e cott,onseetl-meal was 0.1000- 0.0682j = 0 . 0 3 1 7 j g r a m . B u t t h e hlethods of Analysis, A. 0 . .4.C., Bull. 107, revised. p. 5 6 This crude fiber includes ash ingredients of the fiber. The ;irh i i . honevei, so small in amount as to be negligible, unless I large prolitirtion of hulls is contained in the cottonseed-meal. Only in the latter c d i r ~volild it be necessary to take the ash of the fiber into account i n calculating thc amount of lint in the meal. "Cross-Brvan'sMethod for Cellulose"--Cohn'~ ''Tt..I>.rrid R e x x e . i t ~ , ' ' p. 5 2 . 1
2
