CH. X] 



REAGENTS AND THEIR PREPARATION 



349 



(B) 82% alcohol made by mixing 5 parts of 95% alcohol with i 

 part of water. 



(C) 67% alcohol made by mixing 2 parts of 95% alcohol with i 

 part of water. See also 537-538. 



541. Alcohol (methyl), CH 5 OH. Methyl alcohol or wood alcohol 

 is much cheaper than ethyl or grain alcohol on account of the 

 revenue tax on ethyl alcohol. It answers well for many microscopic 



FIG. 210. GLASS-STOPPERED BOTTLES FOR THE MORE USUAL GRADES OF ALCOHOL 

 USED IN MICROSCOPY. 



purposes. It has been refined so carefully in recent years that the 

 disagreeable odor is not very noticeable. 



542. Denatured alcohol. This is ethyl or grain alcohol ren- 

 dered undrinkable by the addition of wood alcohol and benzine (grain 

 alcohol, 89!%; methyl alcohol 10%, and benzine i%). In some 

 cases the denaturing substances are somewhat different, but all render 

 the alcohol unusable for drinking. It is then free from internal 

 revenue tax. 



In Great Britain "Methylated Spirits" consists of grain alcohol 

 with 10 % methyl alcohol. This is used very largely in microscopic 

 work. In America the addition of the benzine renders denatured 

 alcohol also unfit for histological purposes if it is to be diluted. The 

 addition of water makes it milky. If methyl alcohol alone or combined 

 with pyridin or some other substance wholly soluble in water were 

 used as the denaturing substance, denatured alcohol could be used 

 in microscopic work for all the grades. That denatured as indicated 

 above can be used only in full strength or very slightly diluted. 



