Nov., 1917
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
whether he may safely continue t h e staining with t h e red for 6 or possibly 7 minutes a t 45' C. At first, however, i t is better t o follow t h e directions as given. It is of prime importance t o wash out, or neutralize, every trace of alkali in t h e fibers, as t h e blue is decolorized by alkali. This method of staining will in general give a distinction between pure cellulose fibers and those which contain lignin. Rags, bleached sulfite, soda pulp or a n y thoroughly bleached material are stained red, while unbleached sulfite, groundwood, jute, or any lignified materials are stained blue. T h e principal application lies in t h e estimation of unbleached pulp in book papers. A considerable saving can be made b y using unbleached sulfite instead of bleached, hence i t is important t o know how much unbleached pulp there is in a sheet. KIMBERLY-CLARK COMPANY LABORATORIES NEBNAH,WISCONSIN
SOME SUGGESTIONS CONCERNING THE PREPARATION OF AMMONIUM CITRATE SOLUTION A N D THE DETERMINATION OF INSOLUBLE PHOSPHORIC ACID1 By PHILIP McG. SHUEY
T h e preparation of ammonium citrate solution used in t h e determination of available phosphoric acid is usually looked upon as a very long a n d tedious process. Trery often considerable time is expended in making up t h e solution t o conform with t h e two requisites, neutrality a n d specific gravity, particularly in striking t h e neutral point. Generally t h e method consists of first making a solution of citric acid, a n d t h e n adding ammonia numerous times, in varying quantities, until t h e neutral point is reached, t h u s requiring a test for neutrality after each addition of ammonia, a n d as there is necessarily considerable guess-work attached t o this process t h e operator may a t times overstep t h e mark, making t h e solution too alkaline, requiring t h e addition of more citric acid, a n d probably another long period of numerous additions of ammonia a n d a corresponding number of tests. ' I n order t o save unnecessary loss of time a n d labor, t h e writer found b y experiment t h a t t h e neutral point could be reached at once b y simply calculating t h e amount of ammonia required for a given amount of citric acid, according t o t h e following equation: C3HdOH(COOH)a 3NH3 = C3H40H(COONH4)3. As commercial citric acid contains one molecule of water of crystallization, t h e proportion is 210.08 p a r t s of citric acid t o 5 1 . 1 0 2 parts of ammonia? or a ratio of 1.000of NH3 t o 4.111citric acid. T h e calculation for making u p a solution using 4 lbs. of citric acid has been found, theoretically a n d experimentally, t o be as follows: 4 Ibs. = 1814.37 g., which requires 441.34 g. of NH3. This is equivalent t o 1576.2 g. of aqueous ammonia containing 2 8 per cent NH3. The sp. gr. is 0.900 a t 15' C.,b u t a t t h e time t h e * Presented before the Fertilizer Division a t the 55th Meeting of the
+
American Chemical Society, Boston. September 10 t o 13. 1917.
I045
experiments were conducted, t h e temperature was 23O, a n d t h e sp. gr. therefore 0.89554.' 1576.2 f 0.89554 = 1760 cc. aqueous ammonia required. The above may be summed u p as follows, also t o show ' t h e amount of water required, a n d t h e volume of solution resulting: Commercial Citric Acid. .................... 4 Ibs. Water .................................... 6961 cc. Concentrated Ammonia (28%). .............. 1760 cc. Gain in Volume from Ammonium Citrate. . . . . 791 cc. approximately Total Volume.. ............................ 9512 cc. approximately Specific Gravity, 1.09 a t 20' C. Temperature of both ammonia and water when measured, 23' C.
Commercial citric acid appears t o be very uniform in composition. This is shown by having used t h e above formula several times with practically t h e same result, the solution testing neutral t o corallin in each case. Further, a weighed portion of a sample of citric acid was dissolved in water a n d titrated with a standard caustic soda solution, using phenolphthalein as indicator, a n d t h e result was very nearly I O O per cent in acidity. I n t h e operation of dissolving t h e citric acid, i t is advisable t o a d d t h e ammonia just after t h e water. This materially hastens solution for obvious reasons. There has apparently been a good deal of inconsistency on t h e p a r t of many of us with regard t o a strictly neutral solution. T h e insoluble phosphoric acid in acid phosphate, for example, may be determined with practically identically t h e same result whether or not t h e weighed portion is previously washed with water, and, in practice, t h e washing is rarely done more t h a n a few times, when, in reality, alarge number of washings would be required t o get rid of all t h e acid. Cyanamid, on t h e other hand, is very alkaline, a n d also gives off ammonia in t h e presence of water. A few washings would get rid of b u t a small portion of t h e alkalinity, yet t h e determination of insoluble phosphoric acid has been found t o be extremely close t o t h e theoretical in a large number of experiments i n which Cyanamid was present in considerable amounts, a n d in some cases t h e acid phosphate was present in very small quantity. I n t h e case of acid phosphate t h a t has not been previously washed before digestion, i t is equivalent t o using a slightly acid citrate solution, or one containing approximately 0.5 per cent of free citric acid, which is not enough t o dissolve t h e already strongly acidulated tricalcium phosphate remaining. I n t h e case of ground tankage, whale guano, meat guano, fish, a n d such other materials t h a t have not been strongly acidulated, i t may be important for t h e solution t o be strictly neutral, b u t even sp, t h e usual test as applied with corallin is believed t o be sufficiently accurate, and i t is very doubtful t h a t such a solution would fail t o give concordant results as compared with those found from t h e use of a solution prepared b y t h e use of t h e electric current or some other more sensitive indicator. LABORATORY OB SAVANNAH GUANOCo.. SAVANNAH. GA.
* Sp. gr. variation per degree C.
AND
WILLCOX-IVES % Co.,
= 0.00057 (Lunge and Wienik).
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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 A SUGGESTED FORM OF VISCOSIMETER B y W. C. COPE Received July 21. 1917
T h e usual form of viscosimeter is based on t h e proposition of passing a given quantity of oil or other liquid contained in a cylindrical vessel a t a specified t e m perature through a n orifice of definite dimensions in a variable length of time. The viscosity of t h e liquid under examination, then, is obtained b y comparing t h e time taken for passing a like volume of liquid, such as rape seed oil, through t h e orifice under similar conditions. A criticism of instruments of this kind is: (I) t h e height of column of liquid is variable and t h e first half of t h e liquid collected comes through in less time t h a n t h e second half due t o less head of liquid in t h e viscosimeter; ( 2 ) a n oil of t h e nature and consistency of engine oil a t ordinary laboratory temperature will flow only a few cubic centimeters per minute (to get a n y d a t a on such a n oil t h e temperature must be raised and this will not indicate t h e viscosity at t h e lower temperature) ; (3) time may not be t h e proper medium for a basis of comparison.
Vol. 9, No.
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cone. A tachometer would indicate t h e speed a t a n y time. Temperature of test could be controlled b y carrying out t h e operation in a constant temperature room or enclosing t h e centrifuge in a case in which t h e temperature could be regulated, I t seems t o be impossible t o arrive a t any definite agreement as t o a standard instrument for viscosity while using t h e present system of time variation. It is believed t h a t a n agreement could be h a d on some modification of t h e principle suggested. The suggested form of apparatus is offered with t h e hope t h a t i t will raise discussion a n d accelerate investigation leading t o t h e adoption of a standard viscosimeter. E. I. DU FONT DE NEMOURS & COMPANY EASTERN LABORATORY. CHESTER, PA.
A CONVENlENT AUTOMATIC DEVICE FOR RAPIDLY WASHING PIPETTES B y AUBREY.VAIL FULLER Received September 11. 1917
A suggested form of viscosimeter which is shown in t h e accompanying drawing is based on a different principle and is therefore not subject t o t h e above criticism. It is described as follows: a n a r m of a centrifuge holds a cylindrical or other shaped cup having a n orifice of definite dimensions which is closed by means of a cone needle valve actuated b y a spring. A receiver is a t tached t o t h e cup t o retain any liquid passing through t h e orifice. The receiver is easily detached from t h e cup a n d b y reason of its flat bottom will be perfectly stable when placed on a balance pan. A definite quantity of oil or other liquid under examination is placed in t h e cup a n d t h e centrifuge is whizzed a t t h e desired speed when t h e valve is raised b y passing electric current through a solenoid which excites t h e soft iron core attached t o t h e valve. After a given time t h e current is shut off, whereupon t h e valve is closed b y t h e spring. A definite quantity of liquid will pass through t h e orifice in a definite period of time by varying t h e speed. Hence i t is seen t h a t temperature, time, and volume are constant and force variable. Knowing t h e length of t h e centrifuge a r m and t h e speed of rotation, t h e force required t o pass t h e liquid may be easily calculated b y t h e well-known formula. Viscosity, then, would be measured in terms of acceleration due t o gravity ( g ) , which is a rational system. The centrifuge could be driven b y a motor a n d t h e speed varied by means of a variable speed countershaft
Without doubt t h e piece of glass apparatus in daily use in quantitative analytical work most difficult t o cleanse thoroughly is t h e ordinary transfer pipette. I n order t o surmount these difficulties a n d t o render t h e ppocedure simpler and less time-consuming t h e writer has devised t h e automatic washing apparatus pictured. A is t h e inlet tube, which is connected with t h e water supply either by means of rubber tubing or by being B , B are t h e pipette permanently piped thereto. carriers, provided a t their enlarged ends with short These stoprubber stoppers bored with 3 / ~ - i n holes. . pers are fitted on their lower faces with gate valves C,C, made by cementing small squares of sheet rubber t o t h e m so as t o form a flap over t h e holes, t h e function of these valves being t o prevent t h e escape of water from t h e carrier not in actual use. D is a syphon a n d E a breather pipe, permitting t h e escape of air which would otherwise be compressed as t h e water rises in t h e carriers. The entire pipe system is supported in a copper-lined wooden t a n k , F , provided with a n outlet, G. The operation of t h e device is as follows: The supply t a p is opened until water flows from t h e syphon intermittently as in t h e familiar Soxhlet apparatus. The pipette t o be washed is then placed tip-up in one of t h e carriers. Water rises in both pipette and syphon, b u t on encountering t h e constriction a t t h e tip of t h e former, has its flow arrested, while i t freely rises t o t h e bend in t h e latter and syphonsout,emptying t h e pipette. T h e process repeats itself indefinitely, and one, or several pipettes of different sizes, may be washed simultaneously a n d without attention. I n a two-carrier apparatus as illustrated, a 5 cc. and a zoo CC. instrument may be washed side b y side. The cross-section of t h e syphon pipe is determined
