CI I. /A'] 



PREPARATION OF REAGENTS 



271 



SOME OF THE MORE IMPORTANT REAGENTS USED IN MICROSCOPY 



5 379. Albumen Fixative (Mayer's). — This consists of equal parts of 

 well-beaten white of egg and glycerin. To each 50 cc. of this 1 gram of salicy- 

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

 filtered. For method of use see Ch. X. § 44S. 



fj 3S0. Alcohol (Ethyl), C, H-, O H.— Ethyl or grain alcohol is mostly 

 used for histologic purposes. (A) absolute alcohol (/. 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) S2°„ alcohol made by mixing 5 parts of 95 " n alcohol with I part of 

 water. 



(C) 67% alcohol made by mixing 2 parts of 95",, alcohol with 1 part of 

 water. See also \ 37S-379. 



Fig. 220. 

 Tat um Co.) 



Reagent bottle. {Cut loaned by the ll'hitall 



\ 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 

 ethvl alcohol. It answers well for main 7 microscopic purposes. It has been 

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

 noticeable. 



'I 382. Denatured Alcohol. — This is Ethyl or grain alcohol rendered 1111- 

 drinkable by the addition of wood alcohol and benzine (Grain alcohol, S9 Vo i 

 Methyl alcohol io",,, and Benzine \i%). 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 Benzine 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 



