MILK INSPECTION 195 



are often run by power (see Fig. 56). The smaller sizes may be 

 clamped or screwed to a table, require but little space and are easy 

 to operate. The Babcock bottle for milk-testing (Frontispiece)' 

 holds about 40 cubic centimeters, the neck is graduated from o to 10 

 with sub-divisions of 0.2 per cent. — 2 cubic centimeters being the 

 exact volume of the space between o and 10 — or 10% of 20 cubic 

 centimeters, which volume of milk would be used had milk and 

 melted fat the same specific gravity as water. It happens, however, 

 that 2 cubic centimeters of melted fat weighs 1.8 grams, so in 

 working with the test, 17.6 cubic centimeters of milk (the average 

 volume of 18 grams of milk) are used. It is apparent then that 

 the subdivisions on the stem of the bottle read per cent, direct. To 

 illustrate : Suppose a given sample reads 5 on the neck, the volume 

 occupied by this fat would be just one cubic centimeter and that 

 would weigh 0.9 grams, and 0.9 grams equal 5% of 18 grams, 

 or the per cent, of fat by weight in the milk. 



To make the test : The milk should be well mixed, and both 

 it and the acid should be at a temperature between 6o° and yo° F. 

 The pipette, graduated to 17.6 cubic centimeters, should be filled 

 precisely to this point, by sucking up the milk into it. The milk 

 bottle is to be held in a slanting position and the point of the pipette 

 just introduced into the neck of the bottle (see Fig. 58). 

 By gradually raising the finger from the end of the pipette, the 

 milk is, permitted to flow into the bottle, the last drop being expelled 

 by gently blowing through the pipette. To the milk in the test 

 bottle, 17.6 cubic centimeters of commercial sulphuric acid (specific 

 gravity 1.82) are added in the same manner with the pipette, and, 

 by gently rotating the bottle, the acid and milk are mixed. 



The acid and milk become very hot and care must be taken to 

 mix gradually, and to allow no lumps to collect in the neck. It is 

 well to then let the bottles stand for a few minutes, and mix again 

 by rotating the bottles. 



The bottles are now placed in the machine (it is wise to have 



