EDWARDS, ON CLWANING DIATOMACES. 169 
time until sufficient chlorate is supposed to have been used, 
which is generally known from the deposit becoming per- 
fectly white. Great care must be taken to add the chlorate 
only in small quantities and at distant intervals, or a violent 
explosion will result, shattering the vessel and throwing the 
boiling acid over the clothes and person of the operator. 
A quantity of filtered water in a boiling state is now pro- 
cured, and the sulphuric acid and deposit poured into it in 
small portions. If the water were poured into the acid, the 
heat generated would be so intense that there would be 
danger of rupturing the vessel. After all the deposit has 
been introduced into the water, the boiling is kept up for a 
short time, and then it is allowed to settle. Thus far this 
process is the same as that proposed by Bailey, but is, as I 
have before remarked, incomplete, from the formation of sul- 
phate of potassa, which cannot be entirely removed by water 
alone. 
To complete the cleaning, we allow the deposit to settle, 
and then pour off the supernatant liquid. Sufficient nitric 
or chlorohydrie acid is then introduced to cover the deposit 
to the depth of about an inch, and it is boiled. ‘This acid 
decomposes the sulphate, and forms avery soluble salt, which 
is easily removed by frequent washings with filtered water. 
Phe remaining deposit is washed with filtered water until a 
drop of the liquid does not leave any crystals om evaporation 
on a plate of glass. 
It now consists of sand and Diatomacez only, and should 
be preserved in a mixture of alcohol and water, which prevents 
the Diatoms matting together, as they are apt to do, and 
also will not allow of the formation of Confervz, which form 
in most quiet water. 
