LACTOMETERS. 73 



Vieth's lactometer (Fig. 6) 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 25 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 re- 

 spectively. This auxiliary scale is useless. 



Another form of lactometer, the name of whose inventor is 

 deservedly lost in oblivion, has a scale from to 100, being equal 

 to a specific gravity of 1-000 (water), and 100 being equal to a 

 specific gravity of 1 -029. It is of no practical use in milk testing. 



Still another form is marked M at 1-029, and W at 1-00, the 

 intermediate space being divided into quarters ; this form is a 

 mere toy. 



An instrument has lately been put on the market, which con- 

 sists of a glass tube in which is enclosed a bulb of specific gravity 

 1-029, which floats in milk above this specific gravity, but sinks 

 when the specific gravity is reduced below this figure by watering, 

 by warming, or by excess of cream. It provides a harmless 

 form of amusement, but is of no practical use. 



The best lactometers for use in milk testing are the thermo- 

 lactometer, Soxhlet's, and Vieth's. 



The thermo-lactometer cannot be made very small nor very 

 delicate on account of the enclosed thermometer, and requires 

 a comparatively large bulk of milk ; it is thus more suitable 

 for testing in the dairy than in the laboratory, where samples 

 are often limited. It has, however, the advantage of not re- 

 quiring a separate thermometer and a separate operation to 

 determine the temperature. 



Vieth's lactometer (Fig. 6) may be used in a can and, if the 

 samples are received in cans, as is often the case in a dairy labora- 

 tory, no transference of the sample is necessary. 



Soxhlet's lactometer has a wider scale, and may conveniently 

 be used when greater accuracy is required. 



Galaine's self-correcting lactometer has a metal ball com- 

 pletely filled with chloroform attached to the bottom, the object 

 being to obviate the necessity of correction of the specific gravity 

 for temperature ; the expansion of the chloroform was supposed 

 to compensate the expansion of the milk. Though excellent in 

 theory, it has proved disappointing in practice. 



Beam's lactometer is devised to obviate the difficulty of 

 determining the exact point where the surface of the milk cuts 

 the stem. It consists of a specially graduated lactometer and 

 a float, and the reading is made by observing the point on the 

 stem which corresponds with the uppermost portion of the glass 

 tube of the float. 



