94 



correcting the density was used. D ^= D^ -j- d (.00014 + -^) D = required 

 density; D' =: observed density ; cZ ;= difference in temperature between 15.5°c. 

 and observed temperature. 



After the specific gravity of the distillate was obtained, Allen's tables were 

 used for determining the per cent, of absolute alcohol. 



The apparatus for counting the yeast cells was made by taking a thin strip of 

 brass, cutting an oblong hole through it, then cementing a strip of glass to one 

 side of it, and using a similar strip for a cover on the other side. This gave a 

 chamber of known dimensions, so that when the yeast liquid was placed in it the 

 thickness of the layer was known. To obtain the other two dimensions, a micro- 

 meter having small squares engraved on it was placed in the eye-piece of the 

 microscope, and the value, with a system of lenses then determined. The cell con- 

 tents of a number of these s(iuares were counted, and the average obtained. To 

 determine the number of squares to be counted, countings and determinations 

 were made until the number obtained had no influence on the average. This 

 number of squares was then used on duplicate samples: 



