4 



it first runs through, it can generally be made so by two or three repeated 

 filtrations, after which the washing of the precipitate can be completed. The 

 washed precipitate and filter paper are 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 by 6.25. 

 In working with milk which has been kept with preservatives, the acetic acid 

 should be added in small proportions, a few drops at a time, with stirring and 

 the addition continued until the liquid above the precipitate becomes clear, or 

 very nearly so. 



2. Provisional method for determining albumin in milk. The filtrate obtained 

 in the above operation is neutralized with caustic alkali, three-tenths cc of a 10 

 per cent solution of acetic acid added and the mixture heated to the temperature 

 of boiling water for from ten to fifteen minutes. The precipitate is collected on 

 a filter, washed, and the nitrogen therein determined. Nitrogen multiplied by 

 6.25 equals albumin. 



3. Provisional optional method for determining casein in milk. To 5 grams of 

 milk, 50 cc of a solution of magnesium sulfate saturated at from 40 to 45 

 are added and the mixture heated to about 45, until the precipitate separates 

 and subsides, leaving the supernatant liquid clear. The precipitate is collected 

 on a filter, washed two or three times with the solution of magnesium sulfate 

 prepared as above and at the same temperature, viz, about 45, and the nitrogen 

 therein determined. 



4. Provisional optional method for determining albumin in milk. To the 

 filtrate, obtained by the above process, are added three- tenths cc of a 10 per cent 

 solution of acetic acid and the mixture boiled until the albumin is completely 

 precipitated. The precipitate is collected on a filter, washed as above described, 

 and the nitrogen therein determined. 



Page 37, "3. CHEESE ANALYSIS (PRO VISIONAL METHODS), "omit "(PROVISIONAL 

 METHODS)." 



Page 37, omit all of (a) save caption and insert the following : 

 When the cheese can be cut, a narrow wedge-shaped segment reaching from 

 the outer edge to the center of the cheese is taken. This is to be cut into strips 

 and passed through a sausage-grinding machine three times. When the cheese 

 can not be cut, samples are taken by a cheese trier. If only one plug can be 

 obtained, this should be taken perpendicular to the surface at a point one-third 

 of the distance from the edge to the center of the cheese. The plug should reach 

 either entirely through or only halfway through the cheese. When possible, 

 draw three plugs one from the center, one from a point near the outer edge, 

 and one from a point halfway between the other two. For inspection purposes, 

 the rind may be rejected; but for investigations requiring the absolute amount 

 of fat in the cheese the rind is included in the sample. It is preferable to grind 

 the plugs in a sausage machine, but when this is not done they are cut very fine 

 and carefully mixed. 



Page 37, under (b), omit first and second lines and "tus" of the third line 

 and insert : 



From 2 to 5 grams of cheese should be placed in a weighed platinum or porce- 

 lain dish which contains a small quantity of material like freshly ignited asbestus, 

 sand, etc. 



Page 37, omit under (c) the whole paragraph and insert : 



The extraction tube is prepared as follows: 



Cover the perforations in the bottom of the tube with asbestus, and on this 

 place a mixture containing equal parts of anhydrous copper sulfate and pure, 

 dry sand to the depth of about 5 cm, packing loosely. Cover the upper surface 



