THE 



AMERICAN 

 JOURNAL OF SCIENCE, &c. 



Art. I. — Experiments upon the Solidification of raw Gypsum ; by 

 John P. Emmet, Prof, of Chemistry in the Univ. of Virginia. 



The 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 I 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 connected 

 with the subject of the present communication, and therefore not, 

 perhaps, carried as far as they might have been with advantage, are 

 considered 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, th.^ process may be easily rendered more expe- 

 ditious than when bur^t plaster alone is employed, and the resulting 

 solid, after having j.^on 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 recover their tendency to set, even when the saline 



Vol. XXIIL— No. 2. 27 



