1896 THE MICROSCOPE. 55 



Mounting in Phospliorus, Etc. 



BY ARTHUE M. EDWARDS, M- D. 

 NEWABK, N. J. 



Ever since I began to use Gram Thus for mounting micro- 

 scopic specimens, and the mounting is easy now, doing 

 away entirely with the sticky Canada Balsam, which has 

 not the refractive index of Gum Thus, I have been after 

 some mode of putting up the various specimens I have in 

 solid bodies. Lead chromate has a refractive index of 

 2.50 to 2.97. It is therefore the best object we have for 

 microscopic specimens. Phosphorus has an index of 2.224 

 and comes near to lead chromate. 



I have succeeded in preparing both of these, and will 

 detail exactly how I make them. Premising that the 

 preparations are not patented and can therefore be made 

 by anyone, and I wish they would be made and reported 

 on, for I feel that we have here a means of mounting easy 

 and cleanly and goodly therefore, for the refractive index 

 is high and bacillariaceae, for instance, show nicely when 

 it is used. Any kind of object shows well and we have 

 a medium here attached to the modern immersion ob- 

 jective of oil of cedar, chromate of lead first. I first pre- 

 pare the solution of Grum Thus in alcohol. Cxum Thus 

 is common and sells at about five cents a pound. A lot, 

 about a half a pound, is placed in a wide mouthed bottle 

 and alcohol, the common spirit, is poured on it. It is 

 left to dissolve, being shaken from time to time. I find 

 placing it in the sun in warm weather or otherwise heat- 

 ing it will hasten the solution, after a day or so a satur- 

 ated solution of Grum Thus in alcohol is obtained. It is 

 labeled and put aside to clear by deposition. This it 

 does in two or three days. 



Lead chromate is made by acting of solution of lead 

 acetate (sugar of lead) by means of potassium bichro- 

 mate and the yellow precipitate washed until all of the 



