and for slainhig and gilding Glass. 273 



water, or some other fluid vehicle, by means of which they are 

 spread over the surface of a plate of glass, and when dry, are ex- 

 posed to such a decree of heat as by experience has been found 

 to be suihoieut. The colour is then rub''ed off from the surface 

 of the glass, to which it does not adhere, and those parts of the 

 plate which have been thus covered are found to have acquired 

 a permanent and transparent tin^e or stain, doubtless from some 

 particles of the colour having been absorbed, and fixed in the 

 pores of the glass. 



In all the compositions for staining glass, silver, in some form or 

 other, enters as an essential ingredient; I shall therefore begin by 

 describing the different preparations of silver that I make use of. 

 Take two or three ounces of pure nitric acid, dilute it with 

 three times its bulk of distilled water, put it into a Florence flask, 

 or any other convenient glass vessel, and add to it refined silver, 

 by small pieces at a time, till the acid, though kept at a warm 

 temperature, refuses to dissolve any more. After standing quiet 

 for some hours, pour off the clear liquor into a clean ground 

 -Stoppered phial, and label it Nitrate of silver. 



Preparations of Silver. 



No. 1. Dissolve common salt in water, and add nitrate of sil- 

 ver, drop by drop, till it ceases to occasion any precipitate; there 

 will thus be obtained a heavy white curd-like substance, which 

 must be well washed in hot water and dried ; by exposure to 

 light, it becomes of a dull purple colour. It is known by the 

 name of muriate of silver, or luna cornea. 



No. 2. Dissolve subcarbonate of soda in water, and add nitrate 

 of silver, as above described. The white precipitate thus ob- 

 tained, when washed and dried, is ready for use. It is called car- 

 bonate of silver. 



No. H. Dissolve subcarbonate of potash in vrater, and proceed 

 precisely as directed for No. 2. The white powder thus obtained 

 is also carbonate of silver. 



No 4. Dissolve phosphate of soda in water, and proceed as 

 already mentioned. The precipitate thus obtained is of a yellow 

 colour, and is called phosphate of silver. 



No. .). Take any quantity of pure silver rolled out into thin 

 plates, and put it into a crucible, together with some sulphur. 

 When the crucible has been a short time on the fire, the sul- 

 phur will first melt, and then will gradually burn away with a 

 blue flame. When the flame has ceased, add some more sul- 

 phur, and proceed as before; then take the silver out, and heat 

 it red in a muflSe ; it will now be white, and very brittle, and, 

 after having been reduced to powder in a mortar, is fit for use. 



No. () Take any quantity of a dilute solution of nitrate of sil- 

 ver, and put into it a stick of metallic tin, warm it a little, and 



Vol. 51. No. 210. Jpril 1818. S the 



