188 [June 19, 



does that produced by a salt of lead and an alkaline peutasulphide. 

 I have, however, obtained a red lead-salt by the reaction of crystal- 

 lized hydrosulphocarbonate of lime and basic acetate of lead, which 

 remains red after drying in the air at ordinary temperatures and ex- 

 posure for weeks to the free atmosphere. I therefore conclude that 

 the blackening of the lead-paper in the above case was not due to 

 hydrosulphocarbonic acid, but to some unknown or unsuspected 

 compound. 



In order to understand this matter fully, I commenced some inves- 

 tigations into the reactions of bisulphide of carbon with metallic 

 oxides and other compounds, a portion of which I have now the 

 pleasure of submitting. 



Red Crystallized Lime- Salt. Slaked lime and bisulphide of 

 carbon are mixed in a close vessel, and allowed to stand for three or 

 four days. The lime at first becomes of a pale primrose-colour, 

 which gradually deepens to a fine lemon-yellow. Water added to the 

 yellow lime gives a solution of a gold-colour, which precipitates salts 

 of lead and silver reddish brown, and salts of mercury brown. These 

 precipitates become black upon standing a short time. If the yellow 

 solution be allowed to remain for a few days in contact with the lime, 

 crystals are formed which will be very small, and so distributed 

 through the lime as merely to give it a fine salmon-colour. 



This lime- salt is of a bright ruby colour, and by the following pro- 

 cess it may be obtained in beautiful crystals. Freshly slaked lime is 

 to be mixed with so much water that, when stirred, it will aggregate 

 into small lumps about the size of peas. These lumps are dried upon 

 a sand-bath till they are hard, and will bear handling without pro- 

 ducing powder. The lumps (quite free from dust) are placed in 

 tubes not more than an inch in diameter. When the lime is cold, bi- 

 sulphide of carbon is poured upon it in sufficient quantity to saturate 

 the lime, and leave a few drops in each tube. The tubes are corked, 

 and allowed to stand for three or four days. Water is then poured in 

 carefully, so as not to remove any powder from the lumps of lime, 

 and the tubes are closed and allowed to stand as long as the crystals 

 increase in size. To obtain the crystals, the mother-liquor is poured 

 off, the mass of lime, &c. is dried at ordinary temperatures, and the 

 crystals are picked out. For success, it is absolutely necessary that 

 the lime should be in lumps, the vessel in which the reaction takes 



