120 



THE ESTIMATION OF FAT. 



The " tare " is used to correct for the small quantity of 

 " extract " obtained from the paper, and to neutralise the effect 

 of any change of weight of the flasks due to handling. 



The connection between the flasks and the extractors and 

 between the extractors and condensers may be made by corks, 

 provided they have been extracted well by ether. 



The tare and the drying of the coils may be omitted, and 

 ordinary ether used in place of dry ether without affecting the 

 results greatly. 



Dry ether is prepared by washing the commercial preparation 

 with water, shaking the washed ether with calcium chloride, 

 and distilling after allowing it to stand over calcium chloride for 

 a day or two. 



Ether sufficiently pure for most purposes may be obtained by 

 distilling (from a water-bath not exceeding 40 C. in tempera- 

 ture) the commercial product from a flask to which a fractionating 

 column is fitted. The first fractions boiling below 34-3 C. and 

 the last boiling above 34-8 C. should be rejected. 



Table XXIII. shows the amount of difference that may be 

 expected between the two modes of procedure. 



TABLE XXIII. PERCENTAGE OF FAT. 



The average difference is found to be 0-06. 



The Maceration Method (often called the Somerset 

 House Method). Dr. James Bell, when Principal of the Inland 

 Revenue Laboratory at Somerset House, on being appointed 

 referee under the " Sale of Food and Drugs Act," devised this 

 method for the estimation of fat and solids not fat in milk, and 

 it has since been perfected at the Government Laboratory. 



The following details of procedure are those employed by the 

 author and Miller, and are essentially those of the Government 

 Laboratory : About 10 grammes of milk are weighed into a 

 basin of platinum or aluminium about 3 inches in diameter and 

 a little over 1 inch high, with a flat bottom, provided with a 

 flat-ended glass stirrer. Two drops of a 0-5 per cent, solution 



N 

 of phenol-phthalein are added, and approximately strontia 



solution run in till a faint pink colour appears. The contents 

 are evaporated to a damp paste on the water-bath, when the basin 



