METPIODS FOR THE ANALYSIS OF SOILS. 

 DETERMINATION OF TOTAL NITROGEN. 



Tage 42, section 8, substitute the following: " From 7 to 14 grams of the soil are 

 placed in a small Kjeldahl digesting flask, about 250 cc capacity, with 30 cc of strong 

 sulphuric acid, or more, if necessary, and 0.7 gram yellow oxid of mercury, and 

 Lolled for an hour. The residue is oxidized with potassium permanganate in the 

 usual way. After cooling, the flask is half filled with water, vigorously shaken, 

 the heavy matters allowed to subside and the supernatant liquid poured into a flask 

 of from 1,000 to 1,200 cc capacity. This operation is repeated until the ammonium 

 sulphate is practically all removed and the large flask is a little more than half full. 

 The distillation of the ammonia from the large flask is accomplished in the usual 

 manner after the addition of the necessary alkali. If a sample is known to contain 

 a considerable amount of nitrate, the modified Kjeldahl method, to include the esti- 

 mation of nitrates, is to be substituted for the one above described." 



METHODS FOR THE ANALYSIS OF FOODS AND FEEDING STUFFS. 



The methods on page 62 (7) under (a), (b), and (c), are made official. The method 

 on page 62 (d) is retained as a provisional method, with the following directions for 

 preparing the reagent: 



Fourth line from bottom take out " 12 per cent.' 7 



Third line from bottom take out " in glacial acetic acid," and insert " acetate made 

 by dissolving 12 grams of pheuylhydraziu acetate and 7.5 grams of glacial acetic 

 acid in sufficient water to make the volume 100 cc." 



For the factors at the top of page 63 for calculating results, the following are sub- 

 stituted: 



Weight of hydra/cone X 0.516 + 0.0104 -f- weight of sample used = percentage fur- 

 furol. 



Furfurol X 1.84 = pentosans. 



Pentosans -H 0.88 = peutoses. 



Furfurol X 1.65 = xy Ian. 



Furfurol X 2.03 =araban. 



METHODS FOR THE ANALYSIS OF DAIRY PRODUCTS. 



CHANGES IN METHODS OF MILK ANALYSIS. 



Page 36 (c). DETERMINATION OF NITROGEN COMPOUNDS. 



Add at end of paragraph the following: 



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

 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 

 mercuric chlorid to 2,000 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 C., 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 decantation, and then transfer pre- 

 cipitate completely to filter. Wash once or twice on filter. The filtrate should be 

 dear, or very nearly so. If the filtrate is not clear when it first runs through, it can 

 generally bo made so by two or three repeated nitrations, after which the washing of 

 the precipitate can be completed. The washed precipitate and filter paper are then 

 digested as in the regular Kjeldahl method for the determination of nitrogen, and 

 the process is completed as usual. To calculate the nitrogen into an equivalent 

 amount of casein, multiply the per cent of nitrogen by 6.25. 



In working with milk which has been kept with mercuric chloric!, the arelic 

 acid should be added in small proportions, a few drops at a time, stirring after each 



