203 MARKING CdLOURS FOR tINEN, &C 



pofition, which I expected might be ufed with advantage tn 

 marking piece goods. For this purpofe nothing more is need- 

 ful than to diffolve flowly on the (and bath, and with conftant 

 agitation. One fourth of its weight of afphaltum or bitumen, 

 judaicum well pounded, and afterwards to mix as much lamp 

 black, or any other dark coloured mineral in fine powder, 

 . filch as black lead, galena, or the like. This colour may 

 be had more or lefs thick, by due proportions of the oil 

 of turpentine and bitumen; it prints very well without 

 running, if the proper proportions be attended to, and a 

 little oil of turpentine be added when it becomes too thick. 

 This bituminous colour fupports- the action of alkalies and 

 of oxigen very well, and refills all acids of moderate 

 ftrength. 



As I thought it unnecefTary to continue my experiments on 

 oil colours, I made my experiments on watery compounds in 



the following order. 



Sedion I. 



Flrft marking I dilToIved in four ounces of water one ounce of the fulphate 

 procefs. An im- f Manganefe without its water of cryftallization ; that is to 



preffion is made /....„.—_,, 



of a folution of l a y> it was in the ltate it poflefies when oxigen gas is pro- 

 fulphate of man- cured from the black oxide of manganefe, by means of the 

 with gum^ and 6 lulphuric acid, and by raifing the heat to ignition at the end 

 covered with of the procefs. This folution was thickened with one dram 

 doth beinAhen °^ mie & um a d ra g an m powder, and coloured with lamp 

 dipped in alkali, black, in order to diftinguim exactly the impreffion which 



the manganefe be eaf . made wilh ^ b j atk f a | ine meta ljj c ma f s> f 



precipitates in V, f t ■■ . ■> --'. 



brown oxide which neverthelels, we cannot make effective ule without 



which affords a plunging the end of the marked piece into an alkaline ley, 



Sfcharged by taking care that it (hall not firft be wetted with water, which 



bleaching, or by would carry off the faline matter. The ley may be made 



«ocfffoa. Un * wil{l P otam or f oda > in tne proportion of one part alkali to 



nine or twelve parts water. It may be ufed in the itate of 



carbonate, or rendered cauftic with half a part of quick lime. 



The precipitation of the oxide of manganefe from the marks 



by either of thefe alkaline folutions will take place (exclufive 



of the ftain from the lamp black) of a yellowilh white colour, 



which will become more and more brown by attracting the 



oxigen of the atmofphere. The change of thefe marks to 



the brown, and even to a deeper colour inclining to black, 



will 



