Lll. /.V] PREPARATION OF REAGENTS 271 



SOME OF THE MORE IMPORTANT REAGENTS USED IN MICROSCOPY 



i; 379. Albumen Fixative (Mayer's). This consists of equal parts of 

 well-beaten white of egg and glycerin. To each 50 cc. of this i gram of salicy- 

 late of soda is added to prevent putrefactive changes. This must be carefully 

 filtered. For method of use see Ch. X. $ 448. 



\ 380. Alcohol (Ethyl), C,, H-, O H. Ethyl or grain alcohol is mostly 

 used for histologic purposes. (A) absolute alcohol (i. e. , alcohol of 99%) 

 is recommended for many purposes, but if plenty of 95% alcohol is used it 

 answers every purpose in histology, in a dry climate or in a warm, dry room. 

 When it is damp, dehydration is greatly facilitated by the use of absolute 

 alcohol. 



(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 \ 378-379. 



FIG. 220. Reagent bottle. (Cut loaned by the Whitall 

 Tat urn Co.) 



\ 381. Alcohol (Methyl) C-H.,, O H. 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 purposes. It has been 

 refined so carefully in recent years that the disagreeable odor is not very 

 noticeable. 



'',. 3*2. Denatured Alcohol. This is Ethyl or grain alcohol rendered un- 

 drinkable by the addition of wood alcohol and benzine (Grain alcohol, S$}4% ; 

 Methyl alcohol 10%, and Benzine )4%)- In some cases the denaturing sub- 

 stances are somewhat different, but all render the alcohol unusable for drink- 

 ing. 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 Ben/.ine renders denatured alcohol also unfit for histologi- 

 cal 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 



