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176 REPORT OF THE CHEMIST OF THE 
pearancés, the lactic acid had simply combined with the para- 
casein, forming a compound soluble in slight excess of acid and 
insoluble in neutral solutions. 
(3) Preparation of paracasein lactate obtained from cheese.— 
Cheese about 3 months old was extracted with a 5 per ct. solu- 
tion of sodium chloride. To 6.5 liters of this extract, lactic 
acid was added to the extent of 0.2 per ct. by volume, produc- 
ing a flocculent precipitate that rapidly settled. The precipitate 
was filtered and allowed to drain in order to remove the large 
amount of salt adhering. The filtrate gave no further precipi- 
tate on addition of more lactic acid. The precipitate was com- 
pletely soluble in 0.5 per ct. solution of lactic acid, and this 
acid solution gave an abundant precipitate when neutralized by 
dilute alkali. This neutralization precipitate was filtered, well 
washed with water, and then treated, in every respect, as 
described above in the preparation of the artificial product. In 
this way, 20 grams of each product were obtained. 
Comparison of natural and artificial products. — The old 
method of comparing two products by the results of ultimate 
analysis, in order to establish their likeness or unlikeness, is 
now recognized as faulty, especially in the case of proteid 
bodies. Only by cleavage and by quantitative estimation of cer- 
tain end-products can a reliable basis be found for determining 
the question of similarity of structure in different compounds. 
Determinations of nitrogen, phosphorus, and ash were made 
in the two products. In addition, an amount of each proteid 
weighing 10 grams was hydrolyzed by boiling 14 hours, on a 
sand-bath, under a Liebig condenser, with 60 grams of water 
and 30 grams of sulphuric acid of sp. gr. 1.84. In the resulting 
liquid, ammonia and the hexon bases were determined according 
to the method of Kossel and Kutscher.? The results are given 
in Table III, together with similar figures obtained by Hart 
with casein’? prepared directly from milk by the use of acetic 
acid without rennet. 
Zeit. f. Physiol. Chem. 31: 165 (1898). 
10Tbid. 33: 347 (1900). 
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