282 Dr Hartridge, Colourimeter Design 



adjustment screw. The illuminating system should be fitted 

 beneath the stage so that the instrument may be tilted or moved 

 from place to place without disturbing the alignment. 



For certain purposes it may be found beneficial to employ 

 smaller quantities of liquid than those required in the ordinary 

 colourimeter. I find that a modification in the design of the 

 troughs should make 1 to 2 c.c. of liquid sufficient ; and further, by 

 modifying the optical system as well, as little as "001 c.c. could be 

 worked with. It should be pointed out however that such quantities 

 could only be employed with solutions of considerably greater con- 

 centration than those usually estimated ; e.g. about ten times the 

 usual concentration for 1 c.c, and one hundred times for '001 c.c. 



References. 



(1) Hartridge, Journ. Physiol, l, p. 101 (1915). 



(2) Hartridge, Joum. Qitekett Micro. Soc. Nov. 1919. 



(3) Kober, Journ. Biol. Ghem. xxix, p. 155 (1917). 



