APPARATUS. 143 



The 2-bottle machine has the arms hinged, and clamped in 

 place by a screw, instead of having them in one piece ; it is 

 more easily portable. 



There are many other machines now on the market, which in 

 general principle are much the same as the original Gaertner- 

 HugershofF centrifuges. Some of these are driven by a handle 

 (Fig. 17), which, by means of a worm gearing, imparts a rapid 

 motion to the spindle, and this method of driving finds favour 

 with those who do not mind the extra expense. 



Steam turbines, water turbines, and electro-motors (Fig. 18) 

 are also largely used as the motive power, especially with large 

 machines. 



Apparatus, etc, 1. The acido-butyro- 

 meter is a glass vessel closed by an india- 

 rubber cork, and with a graduated neck 

 divided into ninety divisions ; one di- 

 vision = 0-1 per cent. fat. Every tenth 

 division is longer than the others, and the 

 intermediate fifth divisions are also length- 

 ened slightly to facilitate reading. 



The neck may be either round, as in 

 Gerber's original butyrometers, square 

 section for extra strength, or flat for ease 

 in reading (Figs. 19 and 20). 



A special acido-butyrometer is made for 

 skim milk ; the upper portion of the neck 

 is narrowed, and the divisions are much 

 wider. 



2. The acido-butyrometer for cheese, 

 etc., is open at both ends, and the lower 

 cork carries a small glass cup. 



3. The author's butyrometer stand con- 

 sists of a metal plate pierced with 4, 8, or Fig. 21 -Acid Measure 

 CIA t. i j- T_T_ -J--L. for Gerber Test. 



24 holes, and an india-rubber plate with 



4, 8, or 24 corresponding holes so cut that the butyrometers 

 are slid easily in and out and yet are retained when inserted. 



4. 11 c.c. pipettes for milk with, or without, automatic 

 measurement. 



4a. 3 c.c. pipettes for cream. 



5. 1 c.c. pipette for amyl alcohol. 



6. A water pipette, 10 c.c. in ^ c.c. 



6a. A water pipette for cream, delivering 8-2 c.c. 



7. 10 c.c. bulb pipette for acid. The bulbs prevent the acid 

 from being drawn into the mouth. 



8. Automatic measuring apparatus, or burettes, as an alter- 

 native means of measurement (Fig. 21). 



