1892.] PUBLIC DOCUMENT — No. 33. 85 



allowed to stand until the fat has collected on top ; the 

 water is then drawn off, and a fresh quantity added, and 

 shaken up with the butter. This is continued until 200 to 

 300 cubic centimetres of water have passed through the 

 funnel. The washings are mixed, and made up to 500 cubic 

 centimetres, and the chlorine determined in an aliquot part by 

 means of silver nitrate. From the chlorine the salt is readily 

 calculated. 



(3) Fat. — Two and five-tenths to 3 grams of the fat freed 

 from salt by the above operation (2), and from water by 

 drying in the air bath, are dissolved in ether, and filtered 

 from the curd into a tared flask. The ether is driven off, 

 and the residual fat dried and weighed. In calculating the 

 per cent., allowance is made for salt and water removed. 



(4) Casein. — The residue remaining on the filter in (3) 

 is tested for nitrogen by the Kjeldahl method. The factor 6.33 

 is used in reducing the per cent, of nitrogen found to casein. 



Method for determining Volatile and Non-volatile Fatty Acids 

 contained in Butter. 



The sample is prepared by churning the cream in a suit- 

 able bottle, washing the butter well with cold water, melting 

 at 50 ° C. and filtering from the curd through a hot-water 

 funnel. The fat is then heated in the air bath until free 

 from water. 



The method pursued in the determination of the volatile 

 and non-volatile fatty acids is essentially that described by 

 L. F. Nilson, in " Zeit. f. Anal. Chemie," 28, 2, 176. 



Two and eight-tenths cubic centimetres to 2.9 cubic centi- 

 metres (approximately 2.5 grams) are measured into a tared 

 Erlenmeyer flask of 250 cubic centimetres capacity, and the 

 exact weight determined. Saponification is accomplished 

 by adding 1 gram of potassium hydrate dissolved in 2 cubic 

 centimetres of water, and 5 cubic centimetres of strong (95 

 per cent.) alcohol. The flask is provided with a reflux con- 

 denser, and heated until saponification is complete. The 

 alcohol is then driven off, the last traces being removed by 

 means of the following device : the flask is provided with a 

 double perforated rubber cork, one hole carrying a glass 

 tube reaching nearly to the bottom of the flask and provided 



