FIXING AND PRESERVATIVE MEDIUMS 27 



every order of the Invertebrata is represented. For further 

 details the reader is referred to the complete article by Lo 

 Bianco mentioned in the foregoing footnote, and also to 

 another author mentioned therein — Mr. Arthur Bolles Lee — 

 to whom the present writer is much indebted for some other 

 formulae compiled from his invaluable manual. 



Alcohol. — Amongst the preservatives of the first class, and 

 amid the numberless preservatives to be found recommended 

 in the pages of various manuals, there is nothing which at all 

 compares with, or is so commonly used as a general preserva- 

 tive, as pure alcohol, or rather alcohol of good quality. At 

 Naples, says Lo Bianco, it is considered indispensable, and is 

 used in various strengths. 



Probably the best definition of the various strengths and 

 properties of alcohol is that given by Mr. Arthur Bolles Lee 

 in his Microtomisfs Vade-mecum, pp. 467, 468. This, which 

 is too valuable to abbreviate, is as follows : — 



Absolute Alcohol. — The so-called " absolute alcohol " of commerce 

 is generally of about 98 per cent strength. 



This grade is not necessary for ordinary work. 



95 per cent. Alcohol. — ^This is the average strength of the common 

 strong commercial alcohol, which ranges in general from 94 per cent, 

 to 96 per cent, according to temperature. The strength of this, or of 

 the following, should be determined by means of an areometer (Gay- 

 Lussac's being very convenient), so as to form a starting-point for the 

 following mixtures. 



This is the usual grade for dehydrating before clearing. It is the 

 highest grade that should be used for dehydrating celloidin sections. 



90 per cent. Alcohol. — Made approximately by taking 100 vols. 

 95 per cent, alcohol, and 5.5 vols, water. 



This is the usual strength of the strongest commercial methylated 

 spirit, which (if free from mineral naphtha) may be taken instead of 

 pure alcohol for common work. If naphtha be present the alcohol 

 becomes turbid on the addition of water. Oil of bergamot will clear 

 from this grade. 



