of Roman Glass and Sealing-wax. 123 



on a glass dish, and it proved to be sulphate of soda with a 

 small quantity of sulphate of lime, without any salts of potash. 

 The result of this is, that the glass consists of 



1. Silica 4. Oxide of manganese 7. Alumina. 



2. Soda 5. Oxide of iron 



3. Lead 6. Lime 



Of these constituents the silica formed about two thirds, and 

 the other substance the remaining third of the whole mass. 



II. Sealing-was. 



A piece of a light brown-red waxy substance appeared to be 

 a fragment of sealing-wax of which the Romans had made 

 use ; for the following investigation seems to favour such an 

 hypothesis. 



The piece weighed about 20 grains, became soft and fluid 

 when heated, burned with a flame, left a carbonized residuum, 

 and by a greater and continued -heat a very small yellowish 

 hard substance. 



a) A part of the substance was rubbed small, and the red- 

 dish powder brought into contact with cold aether. This was 

 poured off" the undissolved part, the aether evaporated, and a se- 

 diment of a bright yellow colour obtained thereby, which was 

 acted upon by cold alcohol, and left a deposit of a small par- 

 ticle of wax ; and the spirituous solution gave by evaporation 

 a mass very tough when warm and more stiff" when cold, which 

 might be drawn into long threads, was colourless and trans- 

 parent, and most like turpentine or a similar balsam, although 

 nearly without smell. 



b) The residue left after the action of the aether was now 

 boiled in alcohol, and thereby nearly all dissolved : this solution 

 became on cooling very dull, and deposited a large quantity of 

 a white sediment possessing all the qualities of wax. The so- 

 lution left on evaporation some wax and a small quantity of 

 a gummy substance. 



c) The residue which had not been dissolved by this treat- 

 ment was not taken up even by boiling water : it was still of 

 a reddish colour. By the addition oi a few drops of nitric 

 acid it disappeared in part. The nitric solution assumed a 

 whitish colour by the addition of ammonia, and gave with sul- 

 phuretted hydrogen a black precipitate. The nitric acid had 

 dissolved lead, wliich had been probably addetl as colouring- 

 matter to the sealing-wax. 



d) Tlie residue of (c) was still of a brownish colour, was 

 partly dissolved by alcohol and caustic potash, and was pro- 

 bably a yellow gum. When heated it became liquid, and was 

 burned uii, with the exception of a small residuum. 



Qfi ^)The 



