586 
On a New Method of Testing Milk. 
purity of articles of food and drink, and it is reputed to give 
fairly accurate particulars of the quality of milk. I was anxious 
to make some experiments with a view of ascertaining how far 
Feser's lactoscope can be depended upon to indicate with pre- 
cision the percentage of pure butter-fat in milk. 
Having procured the instrument direct from Munich, I tested 
with it a number of samples of milk, the exact composition of 
which I subsequently ascertained by careful chemical analyses. 
On the 23rd of July, 1879, four samples of milk were bought 
in milk-shops : — 
Pno. 1 was milk bought in Holborn. 
No. 2 „ ,, Eagle Street, Holborn. 
No. 3 ,, „ another shop in Holborn. 
No. 4 „ „ New Bond Street. 
On analysis these milks showed the following composition : — 
Composition of Four Samples of Milk. 
No. 1. 
No. 2. 
No. 3. 
No. 4. 
88-71 
3-17 
8-02 
88-11 
4-10 
7-79 
88-96 
3-43 
7-61 
87-20 
3-20 
9-GO 
100-00 
100-00 
100-00 
100-00 
Specific gravity of milk at 18° C. . . 
Percentage of cream by measure j 
thrown up on standing for 18/ 
-61 
1-0285 
per cent. 
9 
•59 
1-029 
per cent. 
13 
•58 
1-028 
per cent. 
8 
l'031 
per cent. 
12 
By measuring the cream which came to the top in the gradu- 
ated narrow measuring glass cylinders or creamometers, two of 
the samples of milk — namely, No. 1 and No. 4 — containing 
almost exactly the same amount of pure butter-fat, 9 per cent, 
of cream were obtained from one sample and 12 per cent, from 
the other ; whilst the sample No. 3, containing rather more 
fat than No. 4, threw up only 8 per cent, of cream, showing 
plainly that the indications of the creamometer, as regards the 
richness of milk in fat, are altogether fallacious. 
Tested in Feser's lactoscope, the four samples showed the 
following percentages of pure butter-fat : — 
Milk. Percentage of pure Butter-fat. 
No. 1 2J to 3 per cent. 
No, 2 3 to 3i „ 
No. 3 21 to 3 
No. 4 2,h to 3J „ 
