1894 THE MICROSCOPE. 115 



A Quick Method of Cleaning Shells of Bacillariacae. 



By ARTHUR M. EDWARDS, M. D., 



NEWAEK, N. J. 



Since I first began studying the Bacillariacae or Dia- 

 tomacese, I have been puzzled to find a process for clean- 

 ing their shells in a manner that would be applicable to 

 all the gatherings both recent and fossil. In the recent 

 we have to deal with the organic matter that is present 

 besides the siliceous shells. In the fossil gatherings we 

 have to treat of the siliceous shells hid in a mass of clay 

 more or less hardened. The recent gatherings are easy 

 enough to clean. We burn only the organic matter off 

 and the siliceous shells are left. With the fossil gath- 

 erings the case is different and more diflBcult to handle. 

 The clay present in more or less- quantity is not so easily 

 removed. Besides it does not dissolve by ordinary 

 methods. Let us see how we proceed in a quick man- 

 ner, for I think I have at last hit that to clean the shells. 



First, we have a recent gathering consisting of bacil- 

 larian shells and organic matter. We pour off the wa- 

 ter first, and thus concentrate the shells. Then we pour 

 them into a two ounce, wide-mouthed bottle. Such a bot- 

 tle I have by me and constantly carry it to make my 

 gatherings in. Into this I put a mass of finely pulver- 

 ized bichromate of potash — enough, when it is dissolved, 

 to leave some dry. This is enough, for the secret is to 

 have enough. The bichromate is cheap enough, about 

 twenty-five cents an ounce at retail, and an ounce will 

 last for a long time. Now we wait for a few minutes 

 until the bichromate is partially dissolved, and then add 

 enough oil of vitriol (sulphuric acid) to super-saturate 

 the water and cause the evolution of bubbles of carbonic 

 dioxide, commonly known as carbocic acid. The action 

 that goes on developes chromic acid, which is dark red, 

 and this acts upon the organic matter and developes 

 carbon dioxide. This action causes heat to be developed 



