304-306] Milk Analysis 181 



heat until the weight is constant. The final weight, minus the 

 weight of the dish, gives the weight of total solids. 



The acetic acid added curdles the milk, and prevents the 

 formation of a scum which would retard the evaporation. 



Fat. — This is the most important determination, and 

 several methods are in use. The first of these is the most 

 reliable. 



304. Adams Process. — A known weight of milk is 

 absorbed by a roll of filter paper. The paper is then dried 

 and extracted with ether. 



This method is the standard one in use by most analysts. 



The roll of filter paper is prepared as follows : Cut a strip 

 of white filter paper 22^ inches long and 2 \ inches wide. 

 Place it on a table, and lay along its surface a piece of string 

 with one end just reaching to the end of the strip and the 

 other end projecting about 6 inches beyond the paper. Now 

 roll paper and string into a coil. The string will prevent the 

 successive coils from touching one another. Tie the free 

 end round the coil, so as to keep the paper permanently in 

 position. 



305. Purification of the Paper. — Fat-free paper may 

 be purchased, but ordinary paper may be rendered practically 

 free by extraction for 1^ hour in the Soxhlet apparatus. 

 If many determinations be required, it is best to soak a 

 number of the strips in several changes of rectified spirit con- 

 taining 10 per cent, glacial acetic acid. The paper should 

 stand at least two hours in this solution. 



306. The Determination. — Suspend the roll of paper 

 from a glass rod by means of the free end of the string. Shake 

 up the sample of milk, and draw off 5 c.c. with a pipette. 

 Allow it to run from the end of the pipette on to the roll, 

 which will completely absorb it. Suspend the roll in the steam 

 oven for about an hour to dry ; then place it in the Soxhlet 



