CHEMISTRY. 223 



ture of the lower algae, occur too frequently to be set down as 

 casual formations, even althou2:h the detinite shape does not stand 

 out so unmistakably as in the Protococcus in the previous diamond. 

 I must confess to the opinion that we have here only a filling out 

 of the organic form, and that the green color, notwithstanding its 

 similarity with that of the Palmellaceas and other of the lower 

 algse, is due to minerals. Among the algae known to me, it 

 reminds me most of the Palmoglcea macrococca (Kiitzing), described 

 b}' A. Brauu in 184:9. — American Athenceum. 



MANUFACTURE OP ARTIFICIAL DIAMONDS. 



The French publication, *• La Propagation Industrielle," pub- 

 lishes a description by M. Caliste Saix of his method of producing 

 colorless, colored, or black diamonds. The system is based on the 

 principle that when a current of chlorine or of hydrochloric gas 

 passes through cast iron in a liquid state perchloride or protochlo- 

 ride of iron is formed, both of which vaporize, the carbon con- 

 tained in the cast iron remaining in both cases perfectly intact, 

 because the chlorine cannot directly unite with it. The crystalliza- 

 tion of the carbon is then within the general rule, for in a body 

 which is dissolved and capable of crystallization, crystallization 

 takes place each time that the dissolving agent evaporates, the 

 size of the crystals depending always on the slowness of the 

 operation. 1st. To obtain colorless diamonds, a current of dry 

 chlorine must be brought to the bottom of the crucible containing 

 the cast iron, by means of a bent tube of china or fire-clay. No 

 organic coloring matter resists the action of chlorine, so that the 

 perchloride of iron in evaporating leaves the carbon to become a 

 colorless crystal. 2d. When it is desired to give the crystal a blue, 

 green, pink, or yellow tint, it is only necessary to mix with the cast 

 iron certain metallic oxides in sufiicient quantity, such as those of 

 chromium, cobalt, and others, or their salts, which will give these 

 colors. 3d. To obtain black diamonds, hydrochloric gas must be 

 broug^ht to the bottom of the crucible in the same manner as for 

 colored or colorless diamonds. Protochloride of iron will be 

 formed, which is volatile, but in this case the carbon will remain 

 black, in consequence of the presence of hydrogen. This ex- 

 plains the fact of all diamonds having the same chemical and min- 

 eral properties, and why in nature the black diamond is found 

 in the greatest quantity, because its formation in alluvial soils 

 requires only the presence of sulphuric acid and marine salt, 

 whereas the others require the presence of particular oxides which 

 are often wanting. To obtain all these varieties of diamonds special 

 furnaces are not necessary ; the crucibles must be covered to prevent 

 the oxidization of the cast iron, which might change the carbon 

 into carbonic oxide, and diminish, in consequence, the yield of the 

 operation. These crucibles should be provided with a small tube 

 reaching outside the furnace, which will enable the chlorides re- 

 sulting from the reaction to be gathered. When the liquid cast 

 iron has been almost completely evaporated out of the crucibles, 



