ALCOHOL VAPOR. 123 



§ 295. Filtration for Deodorization and Decoloration. — This 

 requires the use of animal charcoal^ and should follow the settling 

 and clearing already described. 



Any kind of water filter containing animal charcoal may be 

 used, but the simpler and cheaper forms are sufficient, and the char- 

 coal should be capable of renewal. Such is the earthenware filter 

 made for water under the direction of our colleague. Prof. A. A. 

 Breneman, and for sale by Messrs. Rankin & Son of Ithaca. Un- 

 less the alcohol is clear, the perforated lid should be wrapped in a 

 cloth, and two or more layers of cloth placed over the toj) of the fil- 

 ter, resting on the lid, so that the alcohol may be cleared of sus- 

 pended impurities before it reaches the charcoal. In the absence 

 of a proper filter, a bag of the charcoal may be pushed firmly into 

 a large tunnel ; the tunnel for this purpose should have the smaller 

 end larger than usual. 



§ 296. Crystalline Deposits. — From some specimens, especially brains, strong alcohol 

 extracts substances wbicb are precipitated as white crystals when the percentage of alco- 

 hol is diminished or the temperature l')Wered. The resulting turbidity and clouding of 

 the glass require a thorough washing of the specimen and the jar, and the renewal of the 

 alcohol. The old alcohol should settle in a cool place, and then be filtered through 

 cotton. Even after filtering, it should be used only for hardening and storage. 



When two grades of " old alcohol," whether filtered or not, are mixed, the deposits 

 above mentioned are liable to occur; hence, if a clear mixture is desired, a trial should be 

 made first with small quantities of the liquids. 



§ 297. Strengthening. — So far from increasing, the strength of alcohol is likely to be 

 reduced by the processes of filtration and settling, especially unless precautions are taken 

 against evaporation. A slight improvement may be effected by treatment with quick- 

 lime, and distillation is, of course, an efficient means. The readier method, however, is 

 simply to add to the weaker spirit enough 95 per cent, alcohol to impart to the mixture 

 the required strength (§^ 271, 272). 



When alcohol is purchased at retail, none should be wasted. But if it is obtained free 

 of tax, it is sometimes cheaper to throw away the weaker grades, esi>ecially the dregs after 

 settling, rather than to spend much time in their improvement. 



§ 298. Alcohol Vapor,. — Tlie antiseptic and preservative prop- 

 erties of the vajDor of alcohol may be utilized in two ways : — 



(1) Upon Fresh Specimens. — When a fresh specimen is to be dissected somewhat rap- 

 idly, say within one week in warm weather, or two or three in cold, it will keep with 

 little change if placed in a close vessel at the bottom of which is enough 95 per cent, alco- 

 hol to keep the atmosphere completely saturated with the vapor. In these cases the skin 

 should be removed only as needed, and the exposed parts covered, when not under exam- 

 ination, with cloths wrung out in alcohol. 



(2) Alcoholic Specimens. — Any specimen which has been acted upon throughout by 

 alcohol will keep almost indefinitely in the vapor. Hence, in some cases, especially where 

 a specimen is under daily dissection, after it has been fully saturated vdih alcohol, the 



