(3) Determination. 



Dilute 25 cc of the solution made as directed under (2), (50 cc, if less than 10 

 per cent of potassium oxid be present) to 150 cc, heat to 100, and add, drop by 

 drop with constant stirring, a slight excess of barium chlorid solution. With- 

 out filtering, in the same manner add barium hydrate in slight excess. Filter 

 while hot and wash until the precipitate is free from chlorids. Add to the ni- 

 trate 1 cc of strong ammonium hydrate, and then a saturated solution of ammo- 

 nium carbonate until the excess of barium is precipitated. Heat and add, in 

 fine powder, 0.5 gram of pure oxalic acid or 0.75 gram of ammonium oxalate. 

 Filter and wash free from chlorids, evaporate the filtrate to dryness in a plati- 

 num dish, and ignite carefully over the free flame below a red heat until all vol- 

 atile matter is driven oft 7 . Digest the residue with hot water, filter through a 

 small filter and dilute the filtrate, if necessary, so that for each decigram of K 2 O 

 there will be at least 20 cc of liquid. Acidify with a few drops of hydrochloric 

 acid and add platinum solution in excess. Evaporate on a water bath to a thick 

 sirup and treat the residue with 80 per cent alcohol (specific gravity 0.8645). 

 Wash the precipitate thoroughly with 80 per cent alcohol both by decantation 

 and after collecting on a Gooch crucible or other form of filter. Dry for thirty 

 minutes at 100 and weigh. 



It is desirable, if there be an appearance of foreign matter in the double salt, 

 that it should be washed according to the previous method with several portions 

 of the ammonium chlorid solution of 10 cc each. 



(c) FACTORS. 



For the conversion of potassium platinichlorid to KC1 use the factor 0.3069, 

 to K 2 SO 4 use 0.3587, and to K 2 O, 0.1939. 



METHODS FOR THE ANALYSIS OF DAIRY PRODUCTS. 

 PROVISIONAL METHOD OF SAPONIFICATION. 



Insert on page 28, after (bj), the following: 



Using the same amounts of alkali and alcohol as described above, the saponifi- 

 cation may be conducted on a steam or water bath, the flask being connected 

 with a reflux condenser consisting of a glass tube of not less than one meter in 

 length, or of a shorter condenser cooled by a current of water. 



Page 36, under 2, Milk Analysis; omit first and second sentences and insert : 



1. Heat to constant weight at the temperature of boiling water from 1 to 2 

 grams of milk in a tared flat dish of not less than 5 cc diameter. If desired, 

 from 15 to 20 grams of pure dry sand may be previously placed in the dish. 



Insert 2 before " Babcock Asbestus Method." 



Page 36 (c). DETERMINATION OF TOTAL NITROGEN. 



Add at end of paragraph the following : 



1. Provisional method for determination of casein in cow's milk. The determi- 

 nation of casein in milk should be made when the milk is fresh, or nearly so. 

 When it is not practicable to make this determination within twenty-four hours, 

 add 1 part of formaldehyd to 2,500 parts of milk, and keep in a cool place. 

 Weigh about 10 grams of milk, dilute in a beaker with about 90 cc of water at 

 40-42, and add at once 1.5 cc of a solution containing 10 per cent of acetic 

 acid by weight. Stir with a glass rod, and let stand from three to five minutes 

 longer. Then decant on filter, wash two or three times with cold water by decan- 

 tation, and transfer precipitate completely to filter. Wash once or twice on 

 filter. The filtrate should be clear, or very nearly so. If it be not clear when 



