91 



Prof. Soxhlet has lately changed the test, in so far as he re- 

 quires a determination of the specific gravity of the etheric fat 

 solution. 



For practical purposes Soxhlet's method is too complicated and 

 costly, on account of the price of the apparatus and the large quan- 

 tities of ether required. For laboratories it is much to be recom- 

 mended. 



Marchand's improved method gives also satisfactory results, 

 and would, for practical purposes, have to be preferred to Soxhlet's, 

 since the apparatus is less complicated and costly. 



Rules regarding the Execution of the Lactoiutyrometrio Test. 



1. Milk, ether, and alcohol must be exactly measured in pipettes, 

 each of which is to be used for one of the fluids only. The fluids 

 must be brought into the lactobutyrometer directly from the pi- 

 pettes. 



2. The lactobutyrometer should be well gauged, as in the case 

 of these instruments like inaccuracies are liable to occur as in the 

 lactodensimeters. 



3i A large number of experiments have proved that the strength 

 ► of the alcohol need not be absolutely of a certain standard. Some 

 propose alcohol of 90° Tr., others 91 and 92° Tr. It is certain 

 that an alcohol of from 90 to 92° Tr. gives the best results, and, 

 while the use of an alcohol of less strength is indicated for richer 

 milks, one of greater strength would be required for the examina- 

 tion of a more watery article. 



4. The ether should be very pure 65° == 0.Y25 specific gravity. 



5. The alkali solution should be 36° B., and not more than one 

 drop of it should be used for each 10 c.c. milk. It should never be 

 added to the alcohol and ether mixture, but to the milk before any 

 of these reagents have been added. 



Using these precautions in the examination of a whole milk, the 

 results will always be found to be almost accurate. In examining 

 a milk which has been skimmed, the difference is easily perceptible. 

 A milk, which by the use of the lactobutyrometric test, contains 

 less than 3 per cent, of fat in each of two determinations, should 

 be examined in the laboratory by exact anatysis. 



Shimming and addition of water become evident from the 

 decrease in fat and increase of water. It is referred here to the 



