LACTOMETERS. 213 



fat and total solids, but it requires a considerable amount of 

 time ; if this cannot be done, it is most satisfactory to estimate 

 the fat and to calculate the total solids, as the fat is the most 

 valuable constituent of the milk, and also because the accuracy 

 of this estimation by the LefEmann-Beam methods is rather 

 greater than the accuracy of the total solid determination. In 

 some dairies payment is made according to the amount of fat 

 in the milk ; in this case, the fat estimation should certainly 

 be made. 



The Testing of Milk. 



In this chapter methods requiring less attention in detail than 

 those previously described, and suitable for the use of persons 

 who have not had a thorough analytical training, are described. 

 The results obtained by these methods have not the rigid accuracy 

 which can be obtained by the best gravimetric methods, but 

 determinations approximating sufficiently nearly to the truth 

 can be made, to enable them to be used in practical work. 



Determination of Specific Gravity. 



Lactometers. — This is invariably done in milk-testing by 

 lactometers (see p. 21-1) ; the lactometers used in dairy work are 

 of two kinds, the thermo-lactometer and the ordinary lactometer. 



The thermo-lactometer (Fig. 17) consists of a stem on which is 

 marked a double scale, one part reading the specific gravity, and 

 the other the temperature on the enclosed thermometer ; a 

 cylindrical body ; and two bulbs, the upper one being the bulb 

 of the thermometer, and the lower one (containing mercury 

 or shot) serving for the adjustment. By its means the tem- 

 perature and specific gravity can be read ofi from the same 

 instrument. 



The ordinary lactometer consists of a stem carrying a scale on 

 which the specific gravity is read ; a cylindrical, or globular, 

 body ; and a bulb containing mercury or shot. 



Soxhlet's lactometer (Fig. 18) contains a scale from 25' (1025) 

 to 35'' (r035) divided up into suitable divisions (i or j^). 



Vieth's lactometer (Fig. 19) has a globular body ; it requires a 

 smaller bulk and depth of milk than Soxhlet's, and is suitable for 

 taking the specific gravity in a half-pint can. The scale reads 

 from 26° to 35°. 



Quevenne's lactometer has a scale from 15' to 40°, and 

 marked to show proportions of water added to milk and skim 

 milk respectively. This auxiliary scale is useless. 



Another form of lactometer, the name of whose inventor is 



