1825.] Mr. Badams on a Scarlet Stib-chromate of Lead. 303 



Article X. 



Oti a Scarlet Sub-chromate of Lead, and its Application to 

 Fainting and Calico Printing. By John Badams, Esq. 



(To the Editors of the Annals of Philosophy.) 



GENTLEMEN, Feb. 16, 1825. 



It was announced by Dulong in the Ann. de Chim. so long 

 ago as the year 1812, that by boiling together carbonate of lead 

 and chromate of potash in excess, a red sub-chromate of lead is 

 produced, containing exactly double the quantity of lead m the 

 common chromate. Ten years afterwards, in the same journal, 

 Grouvclle announced the existence of a red chromate, and gave 

 several processes for preparing it, but made no mention of 

 Dulono-'s discovery. It is remarkable that neither of these 

 chemists, nor any subsequent writer, appears to have noticed 

 the important uses to which this substance is applicable. 



Havino- made a variety of experiments upon its properties, as 

 a fast cofour in calico printing, and a durable pigment for artists 

 in oil and water, I wish to give publicity to the advantages 

 which, I think, the arts will derive from its adoption. 



Grouvelle's method of preparing red chromate of lead consists 

 in boiUng the common yellow chromate with potash ; for prac- 

 tical purposes this is much more convenient than Dulong's pro- 

 cess, and gives a very fine colour. By some unaccountable 

 blunder, however, the ingenious author of this formula so com- 

 pletely mistakes the nature of the substance produced by it, that 

 every'step he takes in his analysis to explain the composition 

 of the red chropaate, onlytends'to involve it in deeper obscurity. 

 But he must speak for himself. 



" J'ai analyse comparativement le chromate jaune, le rouge, 

 etle plomb rouge de Siberie. Tons Aonneni exactementXe meme 

 rapport entre fucide et I'oxide. Ce sont des chromates neutres; 

 seulement le chromate rouge contient une petite quantite 

 d'alcah, qui m'a paru etre de 1 a I'o ;" and yet in the very next 

 page, the author contradicts himself, and says, in sumranig up, 

 " 11 suit de lu que I'alcali parait ctre combine a de I'oxide de 

 plomb, et que ceite combiiiaison unie au chromate de plomb, 

 donne lieu au chromate roiige, qui contient ainsi unpeup/ws d' oxide 

 de plomb que le chromate neutre." 



Grouvelle then goes on to assert, that he finds a little alkali 

 (lime) in the native red lead of Siberia, though, as he admits, 

 this very ore becomes yellow on being powdered, which, if it 

 really contained lime, it ought not to do. 



I shall now endeavour to show that the whole of this analysis 

 is erroneous. 



(A.) 100 grains of scarlet chromate of lead made by Grouvelle's 

 process, were digested for half an hour with constant stirring in 



