340 Mr. J. W. Mallet's Report on the Chemical Examination of Antiquities 



six varieties of colour examined, all of which had been laid on upon a uni- 

 form white ground of about the twentieth of an inch in thickness, or perhaps a 

 little thicker, as part of the ground had no doubt been lost in removing the 

 stucco from the walls. The coats of colour were a little thinner, but were not 

 uniform, being thicker in some places than in others ; they were all mixed with 

 an oily substance used in very small quantity, which was soluble in alcliol and 

 ether, reprecipitable from the former on the addition of water ; want of suffi- 

 cient material made it impossible to determine its nature more accuratelj'. The 

 ground or basis upon which the colours were laid consisted of carbonate of 

 lime mixed with a little silica, or rather white siliceous clay, which, as well as 

 the colours themselves, had been carefully and finely ground. The examina- 

 tion of the individual pigments gave the following results: — 



No. 1 was a dull red, almost a brick colour, but somewhat brighter. Heated 

 before the blowpipe on charcoal, it fused into a black shining bead, and in the 

 reducing flame gave globules of a soft, white metal, whicli on examination proved 

 to be lead. Digested in diluted nitric acid it partially dissolved with effer- 

 vescence. The solution gave with hydro-sulphuric acid a black precipitate of 

 sulphuret of lead, and with ammonia, after filtration and lieating, a slight reddish- 

 brown one of peroxide of iron, containing a trace of alumina. On fluxing the 

 residue, insoluble in nitric acid with carbonate of soda, it was found to consist 

 of highly ferruginous silica. Hence this colour appears to be an impure oxide 

 of iron, probably iron ochre, mixed with carbonate of lead ; or possibly may 

 have been red lead, mixed with ground hasmatite, the former having altered in 

 chemical composition in the lapse of time, by the action of air and moisture, &c. 



No. 2. A pale yellow, verging on Naples yellow or yellowish white. Before 

 the blowpipe it behaved nearly in the same manner as the red, but became much 

 darker by the first application of the heat, before fusion. Treated in the same 

 way as the last, it proved to be a light yellow ochre, mixed with a large pro- 

 portion of ceruse, and containing a good deal of the oily matter with which the 

 colours appear to have been mixed. Originally it may have been of an orange 

 colour, and the lead, as in the last case, in the state of red lead. 



No. 3. A light blue ; the only one of tlie colours which had any pretensions 

 to brilliancy. It invariably occuiTed over a coat of the red, No. 1 ; which 

 probably was picked out or cut through in some places, so as to produce a 



