6«6 ANNUAL REPORT OF THE Off. Doc. 



Quevenne lactometer settles in milk at 60 degrees F. to the point 

 marked 29, it means that the specific gravity is 1.020, the lowest 

 limit allowed for normal milk. (See Fig. 25.) 



(3.) Board of Health Lactometer. — Many city milk inspectors in 

 the eastern and middle States used the so-called New York Board 

 of Health lactometer. This does not give the specific gravity of 

 milk directly, as does the Quevenne lactometer, but the scale is 

 divided into 120 equal parts, the mark 100 being placed at the 

 point to which the lactometer sinks when lowered into milk having 

 a specific gravity of 1.029 (at 60 degrees F.), this being taken as 

 the lowest limit of specific gravity in the case of normal milk of cows. 

 The zero mark on the scale shows the point to W'hich the lactometer 

 will sink in water. The distance between these two points is divided 

 into 100 equal parts and the scale is continued below the mai'k 

 to 120; 100 degrees on the Board of Health lactometer corresponds 

 to 29 degrees on the Queveune lactometer, and the zero mark for 

 both is 1, the specific gravity of water; hence, we can change the 

 degrees on the Board of Health lactometer into degrees of the Que- 

 venne lactometer by multiplying the readings of the Board of Health 

 lactometer by .29. Tables are often given showing the equivalents. 



(4.) Value of Lactometer in Detecting Adulterated Milk. — The 

 value of the lactometer in detecting adulterated milk was formerly 

 greatly overestimated. Taken by itself, the lactometer is thoroughly 

 unreliable and misleading. Its proper use in milk inspection is 

 simply to indicate whether a sample is suspicious and ought to be 

 further investigated by detailed chemical analysis. As pointed out 

 above, a milk could be both skimmed and watered and yet the lac- 

 tometer would show it to be entirely normal. 



(5.) Use of Lactometer in Estimating Solids of Milk. — By finding 

 out the specific gravity and per cent, of fat in milk, it is possible, 

 by making a few calculations, to ascertain quite closely the amount 

 of total solids in milk and the solids-not-fat. Babcock has given 

 useful rules for this purpose, which are as follows: 



Rule 1. To find the per cent, of solids-not-fat in milk, add two- 

 tenths of the per cent, of fat to one-fourth of the lactometer reading. 



Rule 2. To find the per cent, of total solids in milk, add one and 

 two-tenths times the per cent, of fat to one-fourth of the lactometer 

 reading. 



These rules give good results when applied to lactometer readings 

 between 26 and 36 and to milk containing 2 to 6 per cent, of fat. 



Example 1. A milk contains 4 per cent, of fat and the Quevenne 

 lactometer reading is 32. What it the amount of total solids in 

 the milk? 



