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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 E N G I N E E R I N G C E E M I S T R Y
Vol. 9, No.
II
LABORATORY AND PLANT METHOD OF STAINING TO DISTINGUISH BETWEEN BLEACHED AND UNBLEACHED SULFITE POLPS By CHARLESG. BFZGHT
The principle of t h e method is first t o stain t h e fibers with Cross and Bevan's ferric ferricyanide solution, which colors t h e unbleached sulfite green on account of t h e lignin contained in it, and leaves t h e bleached sulfite colorless. This alone gives a good distinction, b u t by subsequently staining with a red substantive dyestuff, t h e green of t h e unbleached is changed t o a very pure blue, t h e bleached being colored red, .thus giving a most striking contrast. The problem is t o adjust t h e treatment with t h e two solutions t o bring out t h e sharpest contrast. If t h e treatment with red is too severe some of t h e unbleached fibers are likely t o be colored purplish, or in extreme cases t a k e on a dull, dirty red color. On the other hand, if t h e treatment with ferric ferricyanide is continued for too long a time or a t too high a temperature, t h e reagent has a tendency t o decompose and form a deposit on t h e slide as well as on t h e bleached sulfite, so t h a t t h e latter turns a dull purplish color when subsequently stained with red. T h e results depend on three factors-namely: (I) t h e concentration of t h e solution, ( 2 ) t h e temperature a t which each is applied, a n d (3) t h e length of time each is allowed t o act. I n experimenting with this method these factors were varied separately and t h e combination which gave t h e best results was chosen. T h e solutions are prepared according t o t h e following procedure: FERRIC FERRICYANIDE
SOLUTION A. Tenth Normal FeCls SOLUTION B.
-
2.7 grams FeCla.6HaO per 100 cc. 3.29 grams per 100 CC. Tenth Normal KaPe(CN),
-
After diluting t o t h e mark with distilled water filter through dry filters into clean, glass-stoppered bottlesprstect from dust. Equal volumes of Solutions A a n d B are mixed fresh whenever t h e reagent is used. SUBSTANTIVE RED
...... . . . . . . . . . .. . . .. . . . . ...... . . . . . . .... . . . . .. . .. . ...
0 . 4 gram Benzopurpurin 4B extra (Bayer Co.). , , . 0 . 1 gram Oxamine brilliant red BX(Badische Co.). , . Distilled water , ,, .. , ,, 100 cc. NOTE:Have the water hot and stir in the dyes slowly.
The stain is placed in a tall, narrow cylindrical beaker, which is set into a water bath. The slides are suspended in t h e beaker b y a clamp which holds t h e m a t their upper ends, t h e clamps resting across t h e t o p of t h e beaker. The b a t h is heated by a small Bunsen burner with a pilot flame. T h e burner can be turned on full t o heat t h e b a t h up t o t h e required temperature (35 and 45' C.); then by turning off t h e burner a n d regulating t h e pilot flame t h e b a t h can be kept a t the required temperature without much difficulty. A thermometer is suspended in t h e beaker of stain beside t h e slides. The beaker should be as small as 1 Presented at the Spring Meeting of the Technical Association of the Pulp and Paper Industry, Neenah. Wis., May 24 and 25, 1917. Reprinted from P o p n 30 (Aug. 29, 1917), No. 25, p. 1 1 .
possible so as not t o use up too much stain a t one time. METHOD
OF STAINING
WITH FERRIC FERRICYANIDE
Mix equal volumes of fresh Solutions A and B and heat t o 3 5 O C., regulating t h e water bath so t h a t it will remain within one degree of t h e temperature named, for 1 5 minutes. The dry slide is then dipped in water t o moisten it uniformly, so t h a t air bubbles will not be formed when it is immersed in the stain. If air bubbles are formed t h e fibers under t h e bubbles will not be stained. If dipping in water still leaves bubbles, they can be removed by blowing across t h e slide from t h e edge. The slide is then suspended in t h e stain and left there for 15 minutes a t 3.5' C. It is then removed and washed by dipping in and o u t of a beaker of distilled water six times and repeating the process in a fresh beaker of water. The slide can then be placed wet into t h e red solution, b u t it is perhaps best t o dry it out so t h a t t h e fibers will be stuck on tightly again in case they have been loosened t o a n y extent by t h e treatment. APPLYING THE SUBSTANTIVE RED STAIN
A fresh solution of stain is heated t o 4 5 ' C., and t h e slide, after moistening and excluding bubbles a s before, is suspended in t h e solution for 5 minutes a t 45' C. and immediately washed in two beakers of distilled water. The slide is then dried and a cover glass placed on with a drop of balsam. DIRECTIONS FOR INSURING BEST RESULTS
T o get t h e clearest, brightest results, distilled water must be used throughout, and t h e staining solutions must be fresh. The two solutions for ferric ferricyanide will keep well if placed in separate bottles. Equal volumes are mixed together immediately before using. The red solution should be made freshly each time for t h e best results, as it gets thick and stringy on standing, especially when it is being heated up continually. Staining under t h e conditions described gives on unbleached sufite perhaps t h e deepest blue it is possible t o obtain without depositing blue on t h e slide and on t h e bleached sulfite; the method also produces t h e best red on t h e bleached without turning t h e unbleached purple. Unbleached sulfite from diff ereet mills varies considerably in lignin content, hence some samples stain a deeper blue t h a n others. The foregoing conditions give a satisfactory blue on a sample of high-grade imported unbleached pulp as well as a better color on t h e average run of unbleached pulps, t h e latter being not so well cooked as a rule. With pulp containing more lignin i t is possible t o use a slightly stronger treatment with t h e red and thus get a better color on the bleached without affecting t h e unbleached. After t h e analyst has had a little experience with t h e method he can tell by t h e color of t h e unbleached
Nov., 1917
T H E J O U R N A L O F 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.
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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).
