Lactobutyrometer and Pioscope. 41 
Inventions for testing milk.—Several instruments 
of European invention have been described for the 
quick determination of the fat in milk. Some of 
them make volumetric determinations of the fat or 
cream ; others depend simply upon the opacity of 
the milk. One or two are in common use in 
Germany and Denmark, but, though most of them 
have been introduced in the United States, none 
have come into general use. The more importaut 
of these are the following: 
Marchand’s lactobutyrometer.—This is an instru- 
ment for quickly determining, volumetrically, the 
fat in milk. A measured sample of milk is intro- 
duced into a long glass tube graduated at the 
upper end. A certain amount of acetic acid is 
added and thoroughly mixed with the milk, after 
which ether is added to dissolve the fat, and with 
the aid of a small amount of heat the fat is col- 
lected into the upper graduated portion of the tube 
and read off volumetrically. The lactobutyrometer 
was introduced about 1877, and was used with 
more or less success for a time. In certain sam- 
ples of milk it was found to be difficult to get a 
clear separation of the fat, and in certain other 
samples, notably the milk produced from various 
foods, it was found that the results could not be 
relied upon. 
Heeren’s pioscope.—This is a simple little instru- 
ment designed to test the quality of milk by 
means of its opacity. It consists of a hard rubber 
disc, in the center of which is a small depression, 
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