CLEANING DIATOMS. 289 



valuable material, and possibly the destruction of clothing, 

 he will learn that strong acids and other chemicals are not 

 to be handled like water. Experience makes the process 

 safe and comparatively easy, requiring but a few minutes' 

 attention at a time. No one method will apply in all cases, 

 for some gatherings are imbedded in stone, some cemented 

 with lime, which require special attention, while many 

 gatherings require nothing more than a strong heat to 

 destroy the organic matter and leave them ready for 

 mounting. 



In recent gatherings, when the diatoms are clean, put 

 them into a bottle containing equal parts of alcohol and 

 water, where they may be kept as long as desired. When 

 ready to transfer them to slides, all that is required with 

 most varieties is to dip a few from the bottle with a pipette, 

 to put them on the thin cover-glass, and after placing the 

 glass on a strip of mica or of tintype, keep the whole at a 

 red heat until the organic matter is destroyed and only the 

 shells remain in white powder. 



Another method is to boil for thirty to sixty minutes in 

 strong soapsuds, afterwards washing thoroughly in soft 

 water to get rid of foreign material, such as sand, flocculent 

 matter, &c. On examination of the material, if organic 

 matter be still present, put the mass into a test-tube or 

 other suitable vessel, and, after settling, completely turn 

 off all supernatant water, adding four or five times its bulk 

 of nitric acid, and while boiling throw in small fragments 

 of bichromate of potash to bleach. Some prefer chlorate, 

 but the bichromate is sufficient, and danger of explosion is 

 avoided. When the organic matter has been destroyed, a 

 higher temperature will be required to boil the acid, indi- 

 cating that no more is needed. Probably five or ten 

 minutes will be sufficient. Wash in rain-water, or that from 

 melted ice, until a drop evaporated on a slide shows no 



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