ASSAY OF ARSENICAL DIPPING FLUIDS. 



15 



Milk sugar in fine powder grams . . 100 



Sodium bicarbonate, in powder do 1, 000 



Mix, moisten with dilute alcohol, granulate, dry thoroughly at only 

 slightly elevated temperature, and grind granules to pass a 20-mesh 

 sieve. 



Mix granules with — 



Soluble starch grams. . 100 



Raw potato starch do 75 



Talcum, IT. S. P do. . . . 25 



Compress into tablets of 0.65 gram. 



The practical tablet maker' will be tempted to criticize this formula 

 because it carries so much powder; but since the soluble starch is 

 ruined by wetting it can not be incorporated into the granules, so 

 that there appears to be no escape from this drawback, which at any 

 rate has not prevented the practical preparation of the tablets on a 

 large scale for the use of the bureau." 



The tablets are put up in the 1 -ounce wide-mouth bottle B', fitting 

 into compartment B of the case. 



On the inside of the cover of the case is glued a printed instruction 

 sheet, which is protected by pyroxylin varnish. The instructions 

 read as follows : 



United States Department op Agriculture, 

 Bureau of Animal Industry. 



TEST CASE FOR ARSENICAL BATHS. 



Not to be used on baths prepared from proprietary 

 preparations except on special instruction. 



Keep test fluid in a cool dark place iu glass-stoppered 

 bottles only. 



directions. 



1. Fill clean graduate with bath, setting the top 

 edge of the surface of the bath on the upper gradua- 

 tion (zero or 25 c. c), pour (draining out drops) into 

 clean wide-mouth bottle, add one white indicator 

 tablet, and gently swirl or shake till tablet is nearly 

 all dissolved. 



2. Rinse graduate with clean water, shake out ad- 

 hering drops (or rinse with a little test fluid), and fill 

 to upper graduation (zero) with test fluid, setting the 

 bottom of the curved surface on the mark. 



3. While gently swirling bottle, slowly pour in test 

 fluid from the graduate until the blue or violet color 

 remains permanent for a half minute throughout the 

 entire contents of the bottle after thorough mixing. 

 Avoid excess of test fluid, adding only a few drops 

 at a time toward the end. 



The number of cubic centimeters (reading at the bot- 

 tom of the curved surface) of test fluid added to just pro- 

 duce the color gives the number of hundredths of 1 per 

 cent of arsenious oxid in the bath. 



If the assay is not performed at the vat directly after taking the 

 sample, the same precautions to prevent changes in degree of oxida- 

 tion must be observed as described under "Laboratory Methods for 

 Actual Arsenious Oxid" (p. 4). The scope of application of the 

 method is of course subject to exactly the same limits as laboratory 

 method "A" for actual arsenious oxid (p. 6). 



