USEFUL MICROSCOPE ACCESSORIES 



139 



up as shown. After subsidence has taken place gentle stirring 

 will dislodge any material clinging to the sides of the vessel and 

 this will fall to the bottom. The stopcock is now turned a 

 quarter turn and the liquid emptied out. The stopcock can now 

 be removed with the sediment contained in the conical depres- 

 sion and with but very little of the supernatant liquid. The 

 apparatus is especially useful in cases where fractional separations 

 through variable rates of subsidence can be practiced. 



FIG. 88. Spaeth Sedimentation 

 Glass. 



FIG. 89. Polarization Tube. 

 Bates Type. 



The Bates Polarization Tube. It sometimes happens that 

 an approximate determination is wanted of the specific rotatory 

 power of a substance, but no polarimeter is at hand although 

 a chemical microscope with polarizer and analyzer is available. 

 By introducing a tube of a solution of the substance to be studied 

 into the tube of the microscope, we can convert this instrument 

 into a polarimeter. A convenient form of observation tube for 

 this purpose is the Bates 1 polarization tube, Fig. 89. The tube 

 is filled with a solution of the substance and placed within the 



1 Made by the Bausch & Lomb Optical Company, Rochester, N. Y. 



