340 THE BEGINNINGS OF PHOTOGRAPHY. 



of silvei' as a s^anpathetic ink or as an indellil)le markiiio- ink, ])ut he 

 says nothing- of this, thouoh he mentions the use of silver for writing. 



He gives, however, several recipes for making azure blue pigments 

 from silver, gold, and mercmy, which, in the case of silver, all depend 

 on the formation of an impvire chloride, or double chloride of silver 

 and copper, l\y the action of the vapors of vinegar and sal ammoniac 

 upon thin plates of silver inclosed in a tight vessel and left for some 

 time under warm dung or grape husks, etc. There is no mention of 

 any addition of mercury as recommended 1)V Agricola. 



Angelus Sala, in his Opera Medico-Chymica(16'47), mentions the stain- 

 ing of the hands ])y solution of silver nitrate, but sa3'S it has not the 

 strong corrosi\e action of nitric acid, and when some of the salt was 

 kept in paper for about a j^ear the paper was darkened ]>ut not cor- 

 roded. He also notes that powdered lunar caustic (lapis lunaris) 

 exposed to sunshine appeared like the })lackest ink; this was after- 

 wards quoted by Kircher. He noticed the same change of color if it 

 was mixed with solution of gold. He gives full instructions for cr3\s- 

 tallizing the solution of lapis lunaris. Sala was the lirst to recognize 

 annnonia as a separate l)ody. 



In Glauber's Opera Ch^'uiica (10.5s) there are ^several ]>assages relat- 

 ing to the use of nitrate' of silver solution for staining hard woods like 

 ebony, or for dyeing leather or feathers black, and this is perhaps the 

 hrst mention of the practical use of it for sucli purposes. In Christo- 

 pher Packe's excellent translation of Glauber's works (1(389), Philo- 

 sophical Furnaces, Part II, caption 28, page 26, a method of preparing 

 crystallized silver nitrate is described, and the solubility of the chlo- 

 ride in ammonia is noted as follows: 



The remaining solution which is not crystallized, yi»u may, in a copper vessel 1)y 

 adding sweet water thereto, precipitate over the fire into a calx and then eilnlcorate 

 it and dry it and keep it for other use. Or else you may precipitate the same with 

 salt water and so edulcorate and dry it; and you will have a calx which doth melt 

 by a gentle fire and is of a special nature, and in the spirit of urin, of salammoniak, 

 of hartshorn, of amber, of soot, and of hair it doth easily dissolve, and it may be 

 prepared or turned into good medicines as shortly in our treating of the spirit of 

 urin shall be taught. 



After describing several medicinal preparations of silver, as well as 

 a green oil, made with spirit of sal annnoniac and useful for silvering 

 metals or glass he goes on to mention othtn- uses of silver crystals: 



Lastly, there be many pretty things more effected (besides the medii-inal use) by 

 means of crystal of silver — viz, when you dissolve them in ordinary sweet rainwater 

 you may dye beard, hair, skin, and nails of men or beasts into carnation or pink red, 

 l>rown, or black, according as you have put more or less thereof in the water, or else 

 according as the hair was more or less wetted therewith, wherehy the asjiect of man 

 or beast (which sometimes in several occasions may not be contemned) is changed 

 so that they can not be known. 



