232 Mr. Donovan on the nature and combinations 
attracted my attention. To the naked eye it looked like a coarse 
powder ; but, when examined by the microscope, proved to 
be composed of amorphous crystalline grains. With this 
small quantity of powder I made some trials, which ended in 
exciting farther curiosity. It was probable, that the precipi- 
tate which remained on the filter might be made to furnish 
more grains, and accordingly, after edulcorating the mass, I 
caused boiling water to pass through it. After two hours I 
examined the different washings ; those made with cold wafer 
remained as at first, but those with boiling water had become 
white and turbid, from the suspension of a subtile powder. In 
several hours after, the cloud had disappeared, and displayed 
an abundant and beautiful formation of slender prismatic 
crystals, which glistened with silvery splendor at the bottom 
of the vessel. The mass which remained on the filter had 
become hard, was much diminished, and was verv dense. 
I accounted for the production of crystals by supposing 
that the precipitate, whatever might be its composition, was 
insoluble in cold water, but soluble in very large portions of 
boiling water, and hence the crystalline deposition on cooling. 
Experiment, however, showed, that the residual hard mass, 
even when levigated, boiled with water, and filtered, would 
no longer afford crystals on cooling : and this was a sufficient 
objection to my supposition; for, if one portion of the compound 
be soluble, why not the whole ? 
I observed, that even when the precipitate newly obtained, 
was washed with portions of cold water until it no longer 
altered vegetable colours ; yet the first, second, and some- 
times the third washing with boiling water would, after the 
deposition of the crystals, immediately redden litmus. An 
