CHAP. I.] 



THE PROTEIDS. 



15 



The method of determining the temperature of coagulation is 

 illustrated by Fig. 7. A glass beaker containing water is placed within 

 a second larger beaker also containing water, the two being separated 

 by a ring of cork. Into the water contained in the inner beaker 

 there is immersed a test-tube, in which is fixed an accurately graduated 

 thermometer, provided with a long narrow bulb. The solution of 

 proteid of which the temperature of coagulation is to be determined 



Fig. 7- APPARATUS EMPLOYED IN DETERMINING THE TEMPERATURE OF COAGULATION. 



is placed in the test-tube, the quantity being just sufficient to cover 

 the thermometer bulb. 



The whole apparatus is then gradually heated. With the arrange- 

 ment described the rise in temperature of the contents of the test- 

 tube takes place very slowly and equably throughout. Care being 

 taken to have as good an illumination as possible (the best plan 

 being to place the apparatus between the operator and a well lighted 

 window) the experimenter notes the temperature at which the liquid 

 first shows signs of opalescence ; he afterwards notes again the tem- 

 perature at which a distinct separation of flocculent matter occurs. 



