113 ANATOMICAL TECHNOLOGY. 



often, decomposition is simply retarded by it, wliile the specimen is temporarily protected 

 by arseniate of soda or permanently preserved by means of alcohol. 



Frozen sections and dissections will be discussed later in this chapter. 



§ 259. Arseniate of Soda — Sodium Arsenias. — A saturated solution of this poisonous 

 salt may be used for the injection of specimens which are to be dissected fresh, or for the 

 poisoning of inflated preparations. 



Water dissolves about one fourth of its weight of arseniate ; hence the saturated solu- 

 tion is 30-25 per cent. It should not be allowed to remain upon the dissector's skin 

 longer than necessary. 



Here and elsewhere, when a solution or mixture is mentioned, the menstruum is water 

 unless the contrary is stated. 



ALCOHOL. 



§ 260. Alcohol is almost essential in practical anatomy; its 

 qualities are active, and its management requires constant care. 



General Description. — The alcohol commonly employed for 

 Natural History purposes is, strictly speaking, ethylic alcohol, and 

 a member of a group including several others; the amylic, hutylic, 

 propylic, TnetJiylic, etc. The last named variety will be mentioned 

 again in § 298. 



Ethyl alcohol is colorless, volatile, and inflammable ; it has a 

 vinous odor and pungent taste ; it coagulates albuminous sub- 

 stances and extracts more or less water from organisms immersed 

 in it. Its composition is C2H6O. Its specitic gravity is 796. 



Absolute Alcohol. — The foregoing statements as to composition and specific gravity 

 really apply only to pure or absolute alcohol, that is, alcohol whjch has been freed from 

 water and all impurities. This, however, is quite expensive (about $8.00 per gal.), and is 

 required only for some histological purposes. 



Ordinary or Oommercial Alcohol contains from 5-60 per cent, of water. Most of these 

 mixtures are commonly called alcohols, but some of the grades have also special names, as 

 indicated upon the following Table : — 



§ 261. Table of Specific Gravities op different Percentages of Alcohols 



AT 15|° C, 60° P. 



84, .838, Spiritus rectificatus, Br. 



75, .860. 



60, .896. 



60, .917, [Strong liquors, whisky, etc.] 



49, .920, Spiritus tenuior, proof spirit, Br. 



30, .941, Alcohol dilutum, U. S. 



100, .796, Absolute alcohol. 

 95, .809, [Commercial alcohol.] 

 af, ,817, Alcohol fortius, U. S. 

 89, .825, Lightest spirit obtained by ordi- 

 nary distillation. 

 85, .835, Alcohol, U. S,, spiritus rectifica- 

 tus, rectified spirit. 

 United States Dispensatory, IBth edition, 1880. See also Watts, A, and Baley, A. 



Alcohol as received from the ^varehouse usually contains about 95 per cent, of absolute 

 alcohol ; but that which has been kept for some time, especially if frequently exposed to 

 the air, is apt to range from 90-94 per cent., on account of evaporation and the absorption 

 of water from the air. 



