274 PREPARA TION OF REAGENTS [ CH. IX 



\ 392. Carbol-Xylene Clearer. Vasale recommends as a clearer, xylene 

 75 cc. , carbolic acid (melted crystals) 25 cc. 



\ 393. Carbol-Turpentine Clearer. A satisfactory and generally applica- 

 ble clearer is carbol-turpentine, made by mixing carbolic acid crystals (Aci- 

 duni carbolicum. A. phenicum crystallizatum} 40 cc. with rectified oil of tur- 

 pentine (Oleum terebinthinae rectificatutri) 60 cc. If the carbolic acid does 

 not dissolve in the turpentine, increase the turpentine, thus : carbolic acid 30 

 cc., turpentine 70 cc. 



This clearer is not so good as the preceding for mounting objects which 

 have been stained with osmic acid as the hydrogen dioxid (H.,O.,) present 

 fades the blackened osmic acid. 



'',. 394. Collodion. This is a solution of soluble cotton* or other form of 

 pyroxylin in equal parts of sulfuric ether and 95% or absolute alcohol. 

 Four solutions are used for infiltrating and imbedding. 



(1) i>2% Collodion. 95% or absolute alcohol 100 cc.; soluble cotton 

 3 grams. Let the cotton soak well in the alcohol and then add 100 cc. of sul- 

 furic ether. 



(2) 2>% Collodion. Soluble cotton 3 grams. 95% or absolute alcohol 

 50 cc. After the cotton has become well wet with the alcohol add 50 cc. of 

 sulfuric ether. 



(3) 6% Collodion. For this take 6 grams of soluble cotton and 50 cc. of 

 absolute alcohol. Let the cotton remain in the alcohol over night and then 

 add the 50 cc. of sulfuric ether. 



(4) 8% Collodion. Take 8 grams of soluble cotton and 50 cc. of absolute 

 alcohol. Leave the cotton in the alcohol over night or longer and then add 

 50 cc. of sulfuric ether. 



*The substance used in preparing collodion goes by various names, soluble 

 cotton or collodion cotton is perhaps best. This is cellulose nitrate, and consists 

 of a mixture of cellulose tetranitrate C] 2 H ]( ;(NO.,) 4 O 6 , and cellulose pentani- 

 trate, C i;; Hj-(NO s ) :) C> 5 . Besides the names soluble and collodion cotton, it is 

 called gun cotton and pyroxylin. Pyroxylin is the more general term and in- 

 cludes several of the cellulose nitrates. Celloidin is a patent preparation of 

 pyroxylin, more expensive than soluble cotton. 



Soluble cotton should be kept in the dark to avoid decomposition. After 

 it is in solution this decomposition is not so liable to occur. The decomposi- 

 tion of the dry cotton gives rise to nitrous acid, and hence it is best to keep it 

 in a box loosely covered so that the nitrous acid may escape. 



Cellulose nitrate is explosive under concussion and when heated to 150 

 centigrade. In the air, the loose soluble cotton burns without explosion. It 

 is said not to injure the hand if held upon it during ignition and that it does 

 not fire gun powder if burned upon it. So far as known to the writer, no acci- 

 dent has ever occurred from the use of soluble cotton for microscopic pur- 

 poses. I wish to express my thanks to Professor W. R. Orndorff, organic 

 chemist in Cornell University, for the above information. Proc. Amer. Micr. 

 Soc., vol. XVII (1895), pp. 361-370. 



