MiLK TESTING. 31 
would make the corrected reading for 60° 32.5. The best lac- 
tometers are made with an inside thermometer and these will be 
found very convenient in factory work. 
63. Board of Health Lactometer. 
The Board of Health Lactometer has an arbitrary scale 
reading from 0 to 120; 100 shows a specific gravity of 1.029, which 
corresponds to 29 on the Quevenne scale. This is supposed to 
be the lowest specific gravity of pure milk, the average being 
about 1.032 sp. gr. This scale can be converted into the Que- 
venne scale by multiplying the reading by .29. By so doing one 
can use the Board of Health instrument if a Quevenne is not 
available. 
64. Detecting Watered Milk. 
The solids other than fat make the milk denser and raise 
the lactometer reading, while the fat makes it lighter and lowers 
the reading. Each per cent of fat lowers it seven-tenths of a 
degree. If we multiply the per cent of fat found by the Bab- 
cock test by .7 and add the product to the lactometer reading it 
will give the reading of the milk if the fat were not present. If 
the specific gravity of the other solids is divided by 3.8, the re- 
sult will be per cent of solids not fat. 
For instance, the lactometer reading is 31.5, the tempera- 
ture 65°, and the fat 4 per cent, what is the per cent of solids 
not fat? 
31.5 + .5= 32+ (4 .7=—2.8) = 34.8 + 3.8 = 9.10% 
solids not fat. 
If the solids not fat run below 8.5 per cent it is a poor 
sample of milk and has very likely been watered, especially in 
the case of mixed herd milk. 
If 9 per cent solids not fat be taken as a basis for pure 
milk, and we find but 7.0 per cent, the way to get the amount 
of water added is readily found by use of the formula: 
1009 
I= — 100—29 
About 29 per cent water had, therefore, been added to the 
milk, or expressed in another way: 
7X106 
== 83 per cent, 
