40 DIAT 



•the boiling point, carbonizes the vegetable matters, which, in a 

 charred state, blacken the fluid. The removal of this carbon is 

 to bo accomplished in the form of carbonic acid by the addition 

 to the still boiling acid of oxygen, which, at the very high 

 boiling point of sulphuric acid combines with it, and the gas 

 escapes in ebullition. Nitric acid (NO") may bo slowly poured 

 in until the black or dusky color gives place to the orange hue 

 of nitrous acid (NO 5 ), being what is left of the nitric acid that 

 has parted with two elements of oxygen; or else chlorate of 

 potassa in fine powder, after the manner of Bailey, may be 

 very gradually, and in small doses, dropped into the seething 

 liquid. Upon each contact of the powder a vivid explosion 

 takes place as the carbonaceous par tides ignite and consume. 

 Chlorine is evolved, to the great annoyance of the operator, 

 and sulphate of potassa is added measurably to the sand and 

 Diatoms beneath, But soon all is of pearly whiteness, and the 

 process is at an end. 



The task of cleaning is near its accomplishment; for all that 

 remains to be done is the abstraction of the acid and the wash- 

 ing out of the sulphate of potash. 



Let the tyro be careful, and manipulate with deliberation; 

 for the rapid admixture of sulphuric acid and water occasions a 

 sudden and considerable rise of temperature. Instead of pour- 

 ing or drawung off the hot or cooled fluid, we would recommend 

 that a large beaker glass two-thirds full of hot filtered or dis- 

 tilled water be made ready, and that into the water, by very 

 tardy pouring, or even dropping, the acid, and all it contains, 

 be thrown. When cold, or nearly so, the supernatant fluid 

 must be flowed away, which process is facilitated by holding a 

 glass rod against the beaker's edge to guide the stream, and 

 after repeated washings with distilled water in a fresh beaker 

 (for the sulphuric acid clings to the pot-beaker), the Diatoms, 

 the sand and the amorphous silica alone survive. All is now 

 perfectly clean; but the constituents of the white powder must 

 await separation, and this they can do only in dilute alcohol, be- 

 cause the particles mat or adhere irretrievably in water, in 

 which, also, confervoids speedily arise. We label the vessel, 

 and we choose our own time for isolating the precious forms, 

 observing, however, that the whole sediment has shrunk within 



