7$ ACCOUNT OF BOOKS. 



Des-Mortiers on JReckerchesfitr la Decoloration foontunee du Bleu deP ruffe, 3?c. — 

 Pruffian Blue. Inquiries into the fpontaneous Lojs of Colour in Prujian Blue, 



and the fpontaneous Return of its Colour ; read at a private 

 meeting of the Free Society of Sciences, Literature, and Arts, 

 at Paris, by ,U» R. T. le ftowyer-des-Morticrs, Member of 

 the Society. Paris. 8vo. 32 p. 1801. 



A perfon had made for fale a pretty confiderable quantity 

 of blue paint, confiding of a mixture of white lead, Pruffian 

 blue, and nut oil. To prevent its drying 'he covered it with 

 water fome inches deep, and fet it by till wanted. After a 

 certain time, a perfon coming to buy fome of the paint, he 

 was much lurprifed to find it all white, except at the furface, 

 where the colour was well preferved. He was preparing to 

 •add freffi Pruffian blue to the paint, when, on grinding it in the 

 open air, without any addition, he faw the colour return of 

 itfelf, and on continuing this operation, it became as deep a 

 blue as at firft. He then covered it with oil, fuppoling it 

 would keep better than under water ; but he was difappointed, 

 for the colour^difappeared a fecond time throughout the whole 

 mafs. 



The Society of Phytic and the Arts at Nantes, to whom 

 fome of this paint" was carried in its white Hate, fpread part 

 of it on writing paper, part on wood, and part on the wall of 

 a window. After a longer or fhorter time, the colour of the 

 paint re-appeared with all its luftre, but that on the paper was 

 moft flowly reftored. 



What is the caufe of this phenomena ? Is it the oil, which, 

 by undergoing a change, deftroys the colour of the Pruffian 

 blue ? Is it the air altogether, or one of its conftituent princi- 

 ples, or any other fubftancc mixed or diifolved in it, that re- 

 ftores the colour ? Thefe are the queftions which the author 

 endeavours to anfwer, in pnblifhing the different interefting 

 experiments he has made on the fubjecl, from which he de- 

 duces the following conclufions. 



1. The lofs of colour in the paint is not owing to the de- 

 compofition of the oil, but to a change of furfaces, occafioned 

 by the fubfiding of the mafs, and by the extinction of the lu- 

 1 minous globules in the minute lamjnee and in the pores of the 

 colouring fubftance. 2. Neither the air altogether, nor one 

 of its conftituent principles, nor any thing it contains, is ne- 

 % ceflary 



