44 The Microscope. 



rather more inaTiageable if added to the cement as made from 

 the bleached shellac. 



This purified or bleached variety dissolves very slowly, and 

 the solution is likely to present a curdled appearance due, it is 

 said, to a change produced in the shellac by the absorption of 

 water. A good solution already made, may be purchased from the 

 paint and hardware shops, and evaporated to the desired consis- 

 tency. This makes an excellent colorless and transparent ring, 

 but no better than that formed from the common unbleached gum. 

 The latter, however, is always turbid, and therefore, less attractive 

 to the aesthetic eye. To prepare a clear solution the follow- 

 ing method has been recommended by Prof. W. H. Seaman. I 

 have not tried it. 



To the alcoholic solution is added about one-fourth of its 

 volume of naphtha or of gasoline, and the mixture is shaken 

 several times violently, at intervals of two of three minutes. 

 Let the bottle stand undisturbed for several hours, w^hen the 

 naphtha will be found in a layer at the top with all the insoluble 

 flocculent matters, and the clear alcoholic solution will be 

 beneath. The former should be carefully poured off and dis- 

 carded, or the lower layer may be removed by a siphon. It is 

 this lower layer which is wanted, and it should be evaporated to 

 such a consistency that it will flow easily and smoothly from the 

 brush. The addition of a little castor oil will make it rather 

 more smoothly flowing. 



Personally I am not in the habit of making this cement 

 according to measurement and to rule, except the rule of thumb. 

 I add alcohol to as much shellac as is convenient and leave it to 

 dissolve, diluting or evaporating it as necessity demands. This 

 is not a commendable way. It is better to follow some regular 

 method. The following are the proper proportions : 



Shellac, 60 grammes ; alcohol, 60 grammes ; castor oil, 25 

 grammes ; alcoholic solution of any aniline dye, a few drops. Dis- 

 solve the shellac in the alcohol, add a little of the coloring if 

 desired, and for every 60 grammes of the solution add 25 

 grammes of castor oil. It is recommended that the mixture be 

 heated until the desired consistency is obtained, but heating 

 alcohol is rather dangerous, and should be done with great cau- 

 tion. Spontaneous evaporation will answer the purpose as well. 



It is said that the shellac will become more soluble if treated 



