Extracts from Report on the Analysis of Butter. 183 
chiefly due. In rich butters the proportion of the volatile acids 
is comparatively large, the specific gravity of the fat is high, 
and the percentage of " fixed " fatty acids is correspondingly 
low. 
In getting samples of butter we purposely selected a wide 
range, so as to obtain as far as possible fair representative 
specimens of the different variations that occur in the com- 
position of genuine butters produced under different conditions. 
In short, the samples may be taken to fairly represent the various 
qualities of butter as made and brought to market by farmers 
both in England and Ireland. 
The whole of the samples in Table II. have been tested by 
the specific-gravity method, and it will be seen from the results 
that while a few samples were very poor in quality, and a few 
others exceptionally rich, the great bulk examined were found 
to possess considerable uniformity of composition, the principal 
variations being apparently due to a difference in the method of 
manufacture, the different seasons of the year when made, and 
the various modes of feeding. As might be expected, some of 
the poorest butters were produced by, and obtained from, small 
farmers in Ireland, at a time when there was very little grass 
and food was scarce. 
When the fixed fatty acids test referred to is accurately per- 
formed, the correspondence between the amount of these acids 
and the specific gravity of the fat is so close that it is possible 
to predicate within a few tenths one result from the determina- 
tion of the other. Owing to the pressure of other duties, the 
proportion of fixed fatty acids in each sample was not ascer- 
tained ; but a sufficient number of determinations have been 
made to establish the fact of this correspondence, as will be seen 
in Table II. in the column headed " Percentage of fixed Fatty- 
Acids." A little variation may sometimes arise from the fact 
that the several fixed fatty acids are not always present in 
different butters in exactly the same proportion. 
A noticeable feature in the results recorded in Table II. is 
the great variation in the quantity of water in the different 
butters, the lowest being 4'15 per cent, and the highest 20*75 
per cent. The Devon and Dorset butters, which usually stand 
so high in the market, were found to contain in nearly all cases 
a high percentage of water, and No. 15, which was procured 
from the dairy of a private gentleman, contained as much as 
16*99 per cent., and a second sample, recently obtained from the 
same source, contained 15 - 70 per cent. 
There is another point of interest which we have in some 
measure elucidated, and which has reference to the deterioration 
which certain butters undergo when kept in small quantities in 
