28 TAXIDERMY AND MODELLING 



85 per cent. Alcohol. — Made by taking 100 vols. 90 per cent, 

 alcohol, and 6.5 vols, water. 



Rectified spirit B.P. is a little weaker than this, viz. 84.5 per cent. 



70 per cent. Alcohol. — Made of 100 vols. 90 per cent, alcohol or 

 methylated spirit, and 31 vols, water; or 100 vols. 85 per cent, alcohol, 

 and 23 vols, water. 



Only exceptionally powerful clearers, such as anilin oil, will clear 

 from this grade. This is the proper grade in general for preserving 

 organisms and tissues in ; higher grades should not generally be used 

 unless it is desired to harden. This is the proper grade for washing 

 out borax-carmine stains, corrosive sublimate after fixing, etc. 



50 per cent. Alcohol. — Made by taking 100 vols. 90 per cent, 

 alcohol, and 84.7 vols, water; or 100 vols. 70 per cent, alcohol, and 

 41.7 vols, water. 



This is the strength of proof spirit. 



' One-third Alcohol.' — Made by taking i vol. of 90 per cent, 

 alcohol and 2 vols, water. 



Absolute Alcohol. — This is too strong for ordinary purposes, 

 but has, says Lee, many advantages : it preserves the structure 

 of nuclei (which no other strength of alcohol does), and is one of 

 the most penetrating of all fixing agents, killing and hardening 

 " with such rapidity that structures have not time to get 

 deformed in the process by the energetic dehydration that 

 unavoidably takes place ; " and although it is difficult to pre- 

 serve its strength owing to the rapidity with which it hydrates 

 upon exposure to the air, yet this is partly obviated, says Fol, 

 by keeping a little quicklime in it, which also has the effect 

 of neutralising the acidity often found in commercial alcohols. 

 Mr. Lee mentions that the suspension of strips of gelatin in 

 ordinary alcohol is said to render it absolute. Ranvier's system, 

 however, is to treat 95 per cent, alcohol with cupric sul- 

 phate, calcined, which, after being well agitated, is allowed 

 to settle for a day or two, then filtered and treated afresh, and 

 this is repeated until the addition of cupric sulphate fails to 



