PREPARATION OF REAGENTS 



[CH. VII 



Fig. 167. Slide box for 25 speci- 

 mens. These are cheap and convenient 

 and may be stood on end like books, 

 thus placing the slides in a horizontal 

 position. Smaller boxes, i. e.for j, 6 

 and 12 slides are also made, and mail- 

 ing boxes for a single slide (Bausch & 

 Lomb Co.). 



SOME REAGENTS FOR FIXING, MOUNTING, ETC. 



\ 312. 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 salicylate of 

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

 For method of use see \ 290. 



\ 313. Alcohol (Ethylic). — Ethyl alcohol is mostly used for histological pur- 

 poses. (A) absolute alcohol (i. e., alcohol of T 9 ff 9 g%) 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 1 part of water. 



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

 Grades of Alcohol. It has been found by careful tests that quite accurate 



percentages of alcohol may be obtained by mixing water and alcohol as follows : 

 Pour alcohol into a graduate until the volume of alcohol corresponds to the de- 

 sired percentage. Add water until the volume in cubic centimeters corresponds 

 to the original percentage of the alcohol used. For example, to get 67% from 

 95% alcohol, pour 67 cc. of 95% into a graduate, and add sufficient water to bring 

 the volume up to 95 cc. Far 50% alcohol from 75%, put 50 cc. of 75%' alcohol in 

 a graduate, add sufficient water to make the volume 75 cc. From the change in 

 volume it does not answer to mix given volumes of water and alcohol in these 

 cases. In the first case, if one mixed 75 cc. of 95% alcohol and 20 cc. of water the 

 resulting mixture would be over 75% ; but if sufficient water is added to bring the 

 volume back to the original percentage more than 20 cc. of water is added, that is 

 enough more to compenate for the shrinkage, and the result is approximately 

 accurate. 



Methyl Alcohol is much cheaper than ethyl, and answers well in most micro- 

 scopical processes. It has recently been so carefully refined that the disagreeable 

 odor is very little noticeable. 



Synthol. This is said to be a synthetic form of alcohol. It seems to serve the 

 purpose of alcohol in histology. Absolute synthol is far cheaper for the private 

 worker than absolute ethyl alcohol. 



I 314. Alum Solution. — For muscle dissociated in nitric acid use a satu- 

 rated solution (i. e., a solution in which the water holds all the alum it can. If 

 one adds an excess so that there will always be some undissolved alum in the ves- 

 sel he can be sure the solution is saturated after it has stood a few daj T s. An easy 

 way to get a saturated solution is to take 500 cc. of water and add 100 grams of 

 alum and heat the water in an agate dish. All the alum will be melted, but on 



