The American Journal of Science and Arts (Volume 23) - Softcover

This historic book may have numerous typos, missing text, images, or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1833. Not illustrated. Excerpt: ... 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 minerals 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 experiments, 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 capable of perfect solidification without having undergone the operation of burning, and may perhaps contribute to illustrate or render more available the setting property of this valuable natural production. Raw gypsum, finely pulverized, is capable of undergoing immediate and perfect solidification, when mixed with certain solutions of the alkali potassa. Among those that answer best, may be enumerated caustic potassa, carbonate and bi-carbonate, sulphate and supersulphate, silicate and double tartrate or Rochelle salt. In all these cases, the process may be easily rendered more expeditious than when burnt plaster alone is employed, and the resulting solid, after having been properly dried, does not seem to differ essentially 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 solutions, constantly recover their tendency ...