150 PROCEEDINGS OP THE AMERICAN ACADEMY 



to stand in a cool place until next morning, when the amount of 

 cream was read off. A pipette was then introduced into the cylinder 

 in such a manner that it reached to the bpttom of the vessel, and fifty 

 centimetres were drawn oiF; this was weighed, and gave the specific 

 gravity of the, skim milk. After weighing, the milk was poured into a 

 beaker, one or two drops of acetic acid added, the milk gently wanned 

 until it coagulated, and then allowed to cool again. It was then 

 thrown on a filter, and the first fifty centimetres that ran through were 

 weighed as before : this gave the specific gravity of the whey. 



These two last determinations were made because many authors 

 assert that the specific gravity of skim milk and whey are much more 

 constant than the specific gravity of whole milk. 



Von Baurahauer asserts in his monograph on Dutch cow's milk 

 that he has been unable to obtain clear filtrates when th6 curd was 

 precipitated with acetic acid. I have rarely found any difficulty on 

 this score, when the precaution of heating the milk only a little hotter 

 than from 40° to 50° C. was taken, provided the milk was allowed to 

 become cold before it was filtered. If the milk is allowed to cool 

 completely after coagulation, before it is filtered, it generally filters 

 without any trouble ; but, if poured on the filter before it becomes cold, 

 the fat fills the pores of the filter, and it is almost impossible to do any 

 thing with it. 



Total Solids. Five cubic centimetres were poured into a tared 

 platinum dish and weighed : this latter precaution is necessary, for a 

 pipette cannot be relied upon to always deliver the same quantity of 

 milk, as it will deliver more than enough of a poor milk and not 

 enough of a rich one. This was evaporated to dryness on a water 

 bath, and then dried for an hour in an oven at tlie temperature of 

 105° C. I found that treated in this way the weight became constant 

 at the end of two and a half to three hours from the time the milk was 

 placed on the bath. 



The dishes used have a considerable influence over this result. The 

 size I found to work best were about 65 mm. in diameter and 15 mm. 

 in depth, with the bottom almost perfectly flat, the sides being nearly 

 perpendicular, the angle between the sides and the bottom being 

 rounded. Five centimetres form a layer over the bottom of this 

 dish but little more than 2 mm. thick. When dry, it does not greatly 

 exceed one-eighth of this amount, and tlius forms a film that is very 

 readily dried. 



Fat. After weighing, the dried film is treated with either benzine 

 or ether, which in the course of an hour or two completely removes 



