23 



SEPARATION OF MEAT PROTEIDS. 



Twenty-first Convention, 1904, Bui. 90, Cir. 20. 



PROVISIONAL METHODS FOR THE DETERMINATION OF AMMONIA, CHLORIN, AND PHOSPHORIC 



ACID IN MEAT EXTRACTS. 



Ammonia. By the magnesium oxid method, as described in Bulletin 46, page 21. 



Acidity. Titrate with standard alkali solution, using litmus paper as an indicator. The 

 solution may advantageously be removed from the beaker and placed on the litmus paper 

 by means of a capillary tube. 



Phosphorus. The organic matter should be destroyed by one of the methods given in 

 Bulletin 46, page 12, and phosphoric acid determined by either the gravimetric or volumetric 

 molybdate method described in Bulletin 46, pages 12 and 14. 



Chlorin. Determine chlorin by titration with sulphocyanid, according to Volhard. For 

 ordinary purposes the solution of the ash may be employed. More exact results may be 

 obtained by dissolving about 1 gram of the meat extract in 20 cc of a 5 per cent solution 

 of sodium carbonate, evaporating to dryness, and thoroughly igniting. The residue is 

 then extracted with hot water, filtered and washed, after which the filter and contents are 

 returned to a platinum dish and ignited. The contents of the dish are then dissolved in 

 nitric acid, added to the filtrate, and the chlorin content determined as indicated above. 



INSECTICIDES AND FUNGICIDES. 

 Seventeenth Convention, 1900, Bui. 62. 

 Methods suggested for trial, first year's work. 



Eighteenth Convention, 1901, Bui. 67. 



Methods I and II for the determination of total arsenious oxid 

 were adopted as provisional : 



TOTAL ARSENIOUS OXID. 



Method I. [Made official in 1903.] 



Solutions required: 



Starch solution. To prepare the starch solution, boil 2 grams of starch with 200 cc of 

 water for about 5 minutes. 



lodin solution. To prepare the standard iodin solution, dissolve 12.7 grams of powdered 

 iodin in about 250 cc of water to which has been added 18 to 25 grams of c. p. potassium 

 iodid, and make the whole up to a volume of 1 liter. [Made 2 liters in 1904.] To stand- 

 ardize this solution weigh out 1 gram of the inclosed dry c. p. arsenious oxid; transfer to 

 a 250 cc flask by means of about 100 cc of a solution containing 2 grams of sodium hydrate 

 in each 100 cc, and boil until all arsenious oxid goes in solution; cool; make to a volume 

 of 250 cc and use 50 cc for analysis. 



This 50 cc portion is concentrated by boiling in a 250 cc flask to half its volume and 

 allowed to cool to 80 C. An equal volume of concentrated hydrochloric acid is now added 

 accompanied by 3 grams of potassium iodid, mixed, and the whole allowed to stand for 

 10 minutes (to reduce the arsenic oxid, formed on boiling an alkaline arsenite, to arsenious 

 oxid). The brown solution is then diluted with cold water and an approximately N/10 

 solution of sodium thiosulphate added, drop by drop, until the solution becomes exactly 

 colorless. (This end point is easy to read without the aid of starch.) This solution is then 

 made slightly alkaline with dry sodium carbonate (using a drop of methyl orange to read 

 the change), and made slightly acid with hydrochloric acid, taking care that all lumps of 

 sodium carbonate on the bottom are acted on by the hydrochloric acid. Sodium bicarbonate 

 is now added in excess and the solution of iodin run in, drop by drop, using starch solution 



