LACTOMETER TESTS 203 



on the stem are the second and third dechnals of the 

 numbers of the specific gravity, so that 34 is to be read 

 1.034. For this examination, the temperature of the 

 milk must be 15° C. (60^ F.) ; if it is not, the specific 

 gravity of the milk at 15° C. must be calculated from 

 the specific gravity found and from the temperature, 

 for in milk inspection and analysis this is the standard. 

 AVith the aid of the tables on pages 204 and 21)5, one 

 of which is valid for whole milk and the other for 

 skimmed milk, one can easily compute specific gravity 

 for 15" C. from that found at another temperature. 



If the temperature of the whole milk is IS C, and 

 the lactodensimeter reads 29, one finds in the table, at 

 the intersection of the perpendicular column 1"^ ' (' and 

 the horizontal line 1.029, the number 29.6 ; the specific 

 gravity is therefore e(iual to 1.029() at 15 C. (See 

 tables, pages 204 and 2(15.) 



In several of the lactodensiineters {e.g., Soxhlet's) 

 there is a thermometer in the instrument, whose scale 

 does not show the degree of heat but gives directly the 

 decimal to be added to or subtracted from the reading 

 on the stem of the lactodensimeter, as the s]iecific grav- 

 ity. If the latter number is, for example, 29, and if the 

 thermometer registers 3.5 above zero, the specific grav- 

 ity at 15 C. is 1.1)2935. 



[The so-called New York Board of Health lactometer 

 has an arbitrary scale divided into 120 equal parts. One 

 hundred on this scale corresponds with a specific gravity 

 of 1.029, which was supposed to represent the lowest 

 specific gravity of pure milk, and represents 1.000, the 

 specific gravity of water. If the specific gravity of a 

 sample of milk fell to 90 it was supposed to be 90 per 

 cent, pure, that is, to contain 10 per cent, of added 

 water. But the specific gravity of milk varies so that 

 this cannot be relied on and there is no single advantage 



