AGRICULTURAL EXPRIMENT STATION. 



much less than 8.5 is probably watered. When a standard is 

 adopted the only course to pursue is to consider all milk falling 

 below this standard adulterated. If the milk is not up to the 

 standard it matters not whether it is from poor cows or is diluted 

 after milking, the results are the same. 



It is necessary therefore in order to detect adulterations to 

 determine both the fat and the other solids. For the determina- 

 tion of the former yve would recommend the Babcock test de- 

 scribed in Bulletin No. 3 of this Station and Bulletins Nos. 24 

 and 31 of Wis. Experiment Station, and then the solids not fat 

 can be quite readily and accurately estimated from the specific 

 gravity and per cent, of fat. The specific gravity of whole milk 

 at 60 F. varies from 1 .030 to 1 .034. This means that when a certain 

 volume of distilled water at 60 F. weighs just 1000 lbs the same 

 volume of milk will weigh 1.030 to 1.034 lbs. The solids not 

 fat, namely, the casein, albumen, milk, sugar and mineral matter 

 are the constituents of milk that are heavier than water and 

 therefore cause its greater weight. On the other hand the fat is 

 lighter, consequently the abstraction of fat increases the specific 

 gravity, and the addition of water decreases the specific gravity 

 so one can readily tell whether the milk has been skimmed or 

 diluted with water by these two tests. For example suppose a 

 sample of whole milk contains 4.2 per cent, fat, and has a specific 

 gravity of 1.032. If this milk were diluted one half with water it 

 would contain 2.1 per cent, fat and have a specific gravity of 

 about 1.016, while if it were partially skimmed to contain about 

 2.1 per cent, fat its specific gravity would be increased to about 

 1.0345. 



The Lactometer. 



The instrument we would recommend for taking the specific 

 gravity is the lactometer, which is sufficiently accurate for 

 practical purposes. There are several kinds in use at the present 

 time, all of which are made on the same general principle, viz : 

 A narrow stem attached to an elongated bulb weighted at the 

 bottom so that it will maintain an upright position when floating in 

 the milk, with the stem which is graduated partially submerged. 



The mark on the stem to which it sinks shows the specific 

 gravity. The instrument we would recommend for this purpose is 

 the Quevenne lactometer. The scale on the stem expresses in 

 thousands the weight of the liquid in which it is placed as 

 compared with water. The graduations are usually from 15 to 40 



