120 QUEENSLAND AGRICULTURAL JOURNAL. [1 Fxs., 1899. 
The air is let in at the top by means of slightly loosening the finger, 
and the acid let down to the mark, denoting that up to that point it contains 
10 cc. ‘ 
The test bottle is now inverted ina stand, and the acid run into it. A 
mistake is here very often made, which is to blow the drop or two of acid 
remaining in the tip of the pipette into the test bottle. This is, however, 
wrong, as the pipette is graduated so as to allow of the amount being left in; 
consequently, when it is blown out, an error is introduced ; particularly should 
this be noticed when measuring out the milk, as a drop or two makes some 
little difference in the result. 
Next is put in 1 c.c. of amyl aleohol (on top of the acid), which will 
slightly discolour when coming in contact with the acid. The greatest possible 
care must be observed in measuring the amyl alcohol, as an extra drop or two 
affects the result most remarkably; indeed, if you must make any error in 
measurement, make it in the acid rather than in the alcohol or milk. 
Next comes the milk, which should be let in from the pipette drop by 
drop, not all at once, as some so frequently do. Having put in the measured 
proportions of all the ingredients, the test bottles are corked and well shaken 
before putting into the rotary machine. ‘The test bottles are now submitted to 
centrifugal force in the machine for about two to three minutes, when they 
may be taken out. 
READING THE PERCENTAGE OF FAT. 
The fat will be noticed to have collected on the top of the liquid—that is, 
if the test has been properly performed—and should be of a palish yellow 
colour, although this is not so with the fat of milk under certain conditions of 
feeding, &c. However, it is generally the case. To read off the percentage, 
the fat must be brought upon the graduated scale on the neck of the bottle. 
This is done by pushing in the indiarubber cork. 
Get the bottom of the fat layer even with one of the long graduations, or 
where you see one of the numbers, and then it is a simple matter to read off 
the percentage. Each space between the number represents 1 per cent., which 
is subdivided into ten small divisions each equal to 1 per cent. So that if we 
have three large divisions and five small ones, this would represent 3°5 per cent. 
fat, the composition of a good milk. 
In reading, always see that the bottom of the fat is exactly on one of the 
large marks, and in reading off the decimal percentage read to the bottom of 
the meniscus or air-like bubble which is always present on the top of the fat. 
In making a test of any particular sample of milk, it is advisable always to 
make two tests, which should agree in every particular if the testing is properly 
done and the milk well sampled. 
The ash or mineral matter in the milk usually settles to the bottom of the 
test bottle near the cork in the form of a greyish-white powder. 
Very often it happens that in taking out the bottles (after whirling in the 
machine) the fat is not liquid or clear enough to give a correct reading. This 
is due to a fall in temperature which has taken place. Especially in cold 
weather is this the case ; and another cause of this is that the strength of the 
sulphuric acid is not satisfactory, due, perhaps, to some individual unwittingly 
leaving out the glass stopper of the bottle; and as sulphuric acid has a great 
liking for water, it absorbs the moisture from the atmosphere, and is conse- 
quently depreciated in strength. 
To liquify the fat sufficiently for a correct reading, the bottles (with 
contents) must be placed in hot water of a temperature of about 160 degrees 
fora few minutes, and then put in the machine and whirled for another minute 
to bring to the top any fatty particles which remained in the liquid, due to the 
low temperature at which the test was performed. 
