Scientific Intelligence. — Mineralogy. Ill 



and placed in a large beaker-glass, which contained water enough to 

 cover the two cylinders. In a few months the nitrate of lead had 

 diffused out into the beaker-glass, and formed several beautiful amor- 

 phous compounds on the edge of the cylinder in which the chromate 

 had been placed. In the interior of the cylinder, beautiful pink, 

 highly refractive needles of Rothbleierz (Pb 0, Cr 3 ) were depo- 

 sited, also little dark-red rhombic plates of Melanochroit (3 Pb 0, 

 2 Cr 3 ). The needles of neutral chromate found in this manner 

 attained to three or four millimetres, and then fell to the bottom of 

 the cylinder, where the conditions of their development were want- 

 ing. Had it not been for this circumstance, they would, no doubt, 

 in three or four months, have got to half an inch, or even more. 

 Some crystals of Weissbleierz (Pb 0, C0 2 ) formed in the same 

 vessel, owing, no doubt, to the circumstance that the chromate con- 

 tained some carbonate of potash. In a similar manner I obtained 

 crystals of calc-spar, also rhombic plates of 2 CaO, HO,PO g + 4 HO, 

 and some shining needles, which I believe to be 3 CaO, P0 5 . 



As this method is perfectly general in its principle, and proves 

 applicable to such compounds as carbonate and chromate of lead, we 

 may safely affirm, that the insolubility of a compound will no longer 

 prevent its being prepared in a crystalline form. It appeared in these 

 experiments, as if the great length of time which elapsed before the 

 crystals formed, was owing to the salts not diffusing out rapidly 

 enough ; I therefore modified the form of experiment by placing a 

 vessel full of dry salt inside a large vessel, containing a solution just 

 sufficient in quantity to cover the inner vessel. A large precipitate 

 formed on the undissolved salt, and in a few days little crystals were 

 perceptible in the amorphous mass, which continued to grow as long 

 as the materials lasted. In this way I hope to obtain good-sized 

 crystals of lieavy-spar, calc-spar, sulphate of lead (Schwerbleierz), 

 pyromorphite (3 (Pb 0, P0 5 ) + Pb CI), apatite, &c. By diffusion of a 

 solution of silicate of potash into one of aluminate of potash, I hope to 

 obtain felspar. The crystallization of very soluble compounds may be 

 accomplished by a similar process. Thus, if a solution of sulphate 

 of iron in a beaker-glass is covered with a thin stratum of water, 

 and alcohol gently poured on the top of that, a good and rapid crys- 

 tallization is obtained. It is probable that in like manner crystals may 

 be prepared from an acid, an alkaline, an alcoholic, or an ethereal 

 solution ; and that the separation of two bodies by alteration of the 

 solvent, so often employed in organic chemistry, may thus be com- 

 bined with a separation by means of crystallization. 



The above-mentioned crystals were identified with the minerals, 

 without the aid of chemical analysis; but as in each experiment the 

 number of possible results was limited, and as the crystals agreed in 

 their general chemical deportment and in their physical properties, 

 as well as in their mode of aggregation and geometrical forms, with 

 the minerals named, chemical analysis could hardly have increased 



VOL. LVI. NO. CXI. — JANUARY 1854. M 



