Specific Gravity. 927 



the lactodensimeter is read. The numbers on the lactodensimeter 

 indicate the second, third and fourth decimals of the specific 

 gravity. For each additional degree above 15 C., 0.2 should be 

 added to the reading of the lactodensimeter, and for each degree 

 below 15 C., 0.2 should be deducted. In this way the corrected 

 readings of the lactodensimeter are obtained, before which must 

 be placed 1.0 in order to obtain the specific gravity. The Munich 

 lactodensimeter which is adjusted to a temperature of 15 C. is 

 recommended for general use. 



The specific gravity of the milk may also be determined by 

 the so-called pyknometer. This method is suitable for small 

 quantities of milk. A third method of determination of the specific 

 gravity is Westphal's modification of Mohr's balance. This is so 

 constructed that the lever arm of the balance from its zero point 

 (the axis of the balance) is provided with 9 notches at such dis- 

 tances, that a rider suspended on it indicates from 1 to 10 times 

 its weight, depending upon whether it is pushed towards the 

 end of the arm or towards its axis. Point 10 at the end of the 

 arm is provided with a loop. A weight A, suspended in the loop 

 of point 1, acts on point 1 only as a weight of A/10 at point 10. 



The weights A, Ai, and A 2 , may be mutually interchanged and 

 indicate the integer and the first decimal figure of the specific 

 gravity, depending upon whether they are suspended in the loop 

 or in the notches. The weight B=l/10 of A, and indicates when 

 in the notches 1/100, while C represents 1/10 of B and when in 

 the notches indicates the 1/1000 of the specific gravity. 



By shifting the weight C between two notches the fourth 

 decimal point may also be approximately established. 



Hydrometers made of glass and the use of separate ther- 

 mometers are recommended. 



The specific gravity of market milk varies between 1,029 to 

 about 1,033. 



The increased or decreased specific gravity, as compared with 

 the average specific gravity of the milk of the respective locality, 

 can at the most only be suspected as being caused by dilution with 

 water or by removal of the cream. In case of double adulteration 

 the specific gravity may remain normal. 



After the specific gravity has been determined, the fat content 

 is established by one of the ordinary empiric methods. Gerber's 

 acidbutyrometric method is employed at the milk control station 

 of Munich. 



The following apparatus is needed for this method. 



1. Centrifuge. 



2. Butyrometer (round butyrometer, flat butyrometer, 

 "optical" butyrometer) which is a milk receptacle, ending in a 

 graduated tube into which are poured sulphuric acid, amyl alcohol 

 and milk, and which is closed by means of a rubber stopper. 



3. A 10 c. c. pipette or an automatic measure adjusted 



