220 THE ANALYSIS OF SOLID MILK PRODUCTS. 



but its condition, and affords some clue as to its mode of pre- 

 paration. 



The usual data to be determined are water, solids not fat, fat, 

 salt, and preservatives. It is also occasionally of interest to 

 determine the actual curd, or the casein. 



Water. The most important datum is the percentage of 

 water. As the water is not always equally distributed through- 

 out the mass of butter, especially in butters which have been 

 salted, it is necessary to take precautions to obtain a fair sample 

 a matter of some difficulty. It is not advisable to use a scoop, 

 as water is liable to be squeezed out while forcing it into the 

 lump. Perhaps the fairest way of sampling is to cut the lump 

 into halves, and to take a piece near (not at) one top corner, 

 a second piece in the middle, and a third near the opposite 

 bottom corner. The three pieces should be placed in a wide- 

 mouthed stoppered bottle, melted at as low a temperature as 

 possible, and shaken violently till the mass is nearly solid. If 

 the analysis is to be commenced at once, suitable quantities may 

 be poured out while the butter is still in a semi-liquid condition, 

 and weighed as soon as possible. The water by this means is 

 equally distributed throughout the sample, and a small quantity 

 will be representative of the whole sample. In the case of well- 

 made fresh butter the differences in the distribution of water are 

 small, and a single sample taken from any part of the lump will 

 represent with fair accuracy the whole bulk. Where extreme 

 accuracy is not desired, the melting and shaking of samples of 

 fresh butter may be omitted. 



The water in butter may also be mixed by warming to 

 such a temperature that the butter begins to lose its consis- 

 tency, and stirring vigorously with a stout glass rod. The 

 mixing of salt butter should not be omitted if accuracy is a 

 desideratum. 



The following methods are used for the determination of the 

 water : 



1. About 10 grammes are weighed out into a small porcelain 

 basin provided with a glass stirrer. This is placed over a very 

 small flame, or on a sand-bath, and the butter carefully, but 

 vigorously, stirred till all signs of frothing cease. The tem- 

 perature must be so regulated that spirting is avoided, and that 

 the " curd " does not become appreciably browned by the heat. 

 The basin and its contents are, after cooling, weighed ; the loss 

 of weight indicates water. 



2. A basin is rilled with pumice, which is broken in pieces 

 about the size of a small pea, washed, and ignited ; 2 or 3 grammes 

 of well-mixed butter are weighed in, and the basin placed in a 

 drying oven at 100 C. (212 R), through which a good draught 



