STANDARDIZATION OF PEPTONES 



211 



products of decomposition, contained in it, have a 

 toxic effect. 



To determine the range of rotation, a perfect 

 instrument is necessary. The polarizing apparatus of 

 Schmid and Hansch, of Berlin, is one that answers 



(a] 



FIG. 10. 



(a) Ocular for taking readings; (b) polarization tube; 

 (c) sodium flame; (d) for illumination; (e) battery. 



all the requirements (fig. 10). It allows of read- 

 ings to the hundredth part of a degree. Since 

 everyone makes individual errors in taking readings, 

 i.e., the range of rotation of the same solution is 



