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XXIII. On Pnissiate of Coppef. 



J-N our fourteenth volume, p. 359, wc inserted a sliortpapcf 

 by Charles Hatchett, esq. On the Utility of Pruss'mfe of 

 Copper as a Pigment, which was copied from the Journals 

 of the Royal Institutiaa, vol. i. p. 306. In the 1st number 

 of the 2d vol. of that work, published the 1st of June 1803, 

 \\ as inserted a letter to Mr. Hatchett I'rom Mr. Hume, of 

 Long Acre, v.'hich we overlooked at the time, but which, in 

 justice to both of these gentlemen, we now lay before our 

 readers, some of whom may not have seen the work in 

 Vvhich it originally appeared. 



Letter lo Chaules HatcI-iett, Esq. respecting the Pnis-' 

 siatc of Copper. From Mr. Hume. 



DEAR SIR, 



On many accounts I have chosen to send the following 

 communication to you, rather than lay it before the proper 

 editor of the work to which it alludes; not doubting, if any 

 public notice be deemed proper, your candour and your 

 pen will do meat least as much justice as I deserve. In the 

 last number of the Journals of the Royal Institution, I ob- 

 serve a paper, written with your usual chemical accuracy, on 

 Prussiate of Copper, stating it to be very useful as a pig- 

 ment, &c. I am very confident you were not aware, that 

 the same substance, and for the verv same purpose, had been 

 many years before discovered and prepared by myself; that 

 I have ever since constantly kept it for the use of some par- 

 ticular friends and artists; and have given away and sold of 

 it to numberless other people, who, probably, never till 

 now heard the name of prussiate of copper. I believe, 

 amongst nianv others, two of the present propiietors of 

 the Royal Institution will bear me out and testify to the 

 truth of all this; viz. Mr. William Day, more particularly, 

 and Mr. Collins, enamel painter to the king. The former 

 trcntleman will recollect that, more than ten years ago, I 

 Had made, indo/'d for a very different purpose than painting, 

 a quantity of prussiate of copper; that on begging hixn to 

 try it as a colour, a task he is v^ery competent to, he ap- 

 proved of it and made a very favourable report, especially 

 lespectlng its use in water. Indeed I dare say you are satis- 

 Jied with this single proof; but I shall just add that, from 

 my friend'H recommendation, Mr. Collins began to use it, 

 aiid h*as bccii supplied witii it sinte more than once: the 



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