New York AGRICULTURAL EXPERIMENT STATION. 85 
ing a definite chemical compound. Owing to the variation in 
views expressed by different workers, Hammarsten® took up the 
question and concluded as a result of his work that there was no 
ground for believing that a chemical combination takes place 
between casein and the acid used to precipitate it. He based his 
statement on the fact that by rubbing for several days in a mor- 
tar with different portions of water a precipitate formed by casein 
with an acid, he was able to remove the acid so completely that 
the remaining precipitate gave no test for acid. With the more 
recent knowledge we have of the looser forms of chemical com- 
bination common to proteids and the tendency of such compounds 
to dissociate under conditions less severe than those used by 
Hammarsten, his work can not be regarded as settling the ques- 
tion in such an absolute manner as he indicates. According to 
Hammarsten,* milk-casein contains calcium phosphate in combin- 
ation, and the treatment with acid removes the calcium phos- 
phate, which results in precipitating casein. This view in some- 
what modified forms has been held by Eugling,® Schaffer® and 
Sdldner.? 
In Bulletin No. 214 of this Station, pp. 67-71 (1902), we 
ealled attention in a preliminary way to the fact that we had 
isolated two different compounds formed by casein when treated 
with lactic acid, one of which we called casein monolactate and 
the other casein dilactate. Both compounds are insoluble in 
water. The monolactate is completely soluble at about 130° F. 
(55° C.) in a 5 per ct. solution of sodium choride, while the 
dilactate is practically insoluble. It appears that Hammarsten 
really prepared these compounds but did not recognize what they 
were or their relations to each other. He says:3 “ When we care- 
fully precipitate a very dilute solution of casein with a very 
dilute acid, there is formed a loose precipitate, which dissolves 
completely in sodium chloride to an opalescent liquid.” He adds 
that when too much acid is used, a precipitate is formed that 
is insoluble in sodium chloride solution. 
’Maly Jahresber. d. Thierchem., '7: 160 (1877). 
‘Maly Jahresber. d. Thierchem., 4: 135 (1874). 
‘Landw. Versuchs.-Stat., 31: 392 (1885). 
*Landw. Jahrb. d. Schweiz, 1: 33 (1887). 
‘Landw. Versuchs.-Stat., 35: 351 (1889). 
*Maly Jahresber. d. Thierchem., 7: 163 (1877). 
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