CLEARING OR CLARIFYING REAGENTS. 83 



The following substances are most commonly used : Oil of 

 cloves, a mixture of creosote and turpentine, turpentine, creosote, 

 xylol, cedar-oil, bergamot oil, lavender oil, origanum oil, &c. 



Oil of Cloves has this advantage, that it clarifies rapidly and 

 does not evaporate, so that sections may be left exposed to the air in 

 it for some time. It renders the sections very hard. It, however, 

 is not so satisfactory for aniline dye specimens, as it is apt to abstract 

 their colour. Moreover, it becomes yellow with age. 



Creosote is specially useful for preparations which one does not 

 desire to harden in alcohol ; do not use metallic instruments. 



Creosote and Turpentine. When the fluids are mixed a cloudi- 

 ness appears, but this disappears on keeping. It is much cheaper 

 than clove-oil, but it rapidly evaporates (one part creosote to four of 

 turpentine). 



Xylol is perhaps the best, and is specially useful with aniline 

 dyes. In these cases the balsam Canada or dammar should also 

 be dissolved in xylol. 



Cedar- Wood Oil clarifies very slowly. It does not, however, 

 abstract the aniline dyes, and is used for special purposes, as indi- 

 cated in the context. 



Origanum Oil is used for clarifying sections embedded in 

 celloidin. 



Xylol- Aniline Oil. Equal parts of xylol and aniline are used for 

 clarifying sections under certain conditions without the previous use 

 of alcohol. (Weigert's method, Lesson III.) 



Carbolic Acid and Xylol. A mixture of i part of carbolic acid 

 and 3 of xylol is used to clarify celloidin sections (p. 47). The 

 section can be taken from 70 per cent, alcohol, and does not require 

 to be further dehydrated. To remove the water from the mixture, 

 keep in the bottom of the bottle containing it a thick layer of 

 previously-heated copper sulphate. 



General Remarks. Although several essential oils are used for 

 clarifying purposes, it is not immaterial which one is used. Thus 

 clove-oil may be used for clarifying sections stained with animal 

 or vegetable dyes (carmine), while it is inapplicable for aniline 

 staining, as it dissolves aniline dyes. 



In many cases the result may be obtained more gradually by 

 using a mixture of half alcohol and half essential oil. 



Moreover, clove-oil dissolves celloidin, so that it cannot be used 

 when the section fixed on the slide contains either celloidin or 

 collodion. Oil of bergamot does not dissolve celloidin. 



