THE 
AMERICAN 
JOURNAL OF SCIENCE, &o.. 
Arr. I.—Experiments upon the Solidification of raw Gypsum 3 by 
Joun-P. Emmet, Prof. of Chemistry in the Univ. of Virginia. 
Tue facility with which burnt gypsum sets, when made into a 
paste with water, has rendered it not only conspicuous among min- 
erals but highly useful in the arts; hitherto, however, as far as 1 am 
aware, it has not been supposed that the raw or natural production 
is capable of exhibiting the same property. The following experi- 
ments, although resulting from an enquiry not professedly ! 
with the subject of the present communication, and therefore not, 
perhaps, carried as far as they might have been with advantage, are 
of sufficient importance to receive a distinct notice. 
They” satisfactorily show that native gypsum may be rendered ca- 
pable of perfect solidification without having undergone the opera- 
tion of burning, and may perhaps contribute to illustrate or render 
more available the setting property of this valuable natural pro- 
duction. 
Raw gypsum, finely pulverized, is capable of undergoing imme- 
diate and perfect solidification, when mixed with certain solutions of 
the alkali potassa. Among those that answer best, may be enumer- 
ated caustic potassa, carbonate and bi-carbonate, sulphate and super- 
sulphate, silicate and double tartrate or Rochelle salt. 
In all these cases, the process may be easily rendered more expe- 
ditious than when burnt plaster alone is employed, and the resulting 
Solid, after having been properly dried, does not seem to differ es- 
sentially from that usually obtained, except in composition. ‘There 
does not ‘appear to be any exact point of saturation; for the solid 
masses, when broken up and worked with fresh portions of the solu- 
tions, constantly ge their tendency to set, even when the saline 
Vou. XXIL.—No. 27 
