Queries. — Yellow Dye. — Plumbago, — Lithovasa. 153 



QUERIES. 



To Mr. Tiiloch. 



Sir, An answer to the following queries from some of your 



learned correspondents, will much oblige one of your constant 

 readers. . 



1. Has mercury in the state of vapour ever been combmed 

 with hvdrogen gas ? 



Supposing a quantity of mercury to be heated ni a retort, and 

 in another, hydrogen gas to be produced, from a solution of zinc, 

 could the fumes arising from the two retorts be safely attempted 

 to pass into a heated tube of iron or porcelain ? 



2. Do the precipitates of hme, magnesia, or other pure earths, 

 from watery solutions, assume regular crystallized forms? Have 

 they been subjected to microscopical observation ? 



YELLOW DYE. 



A chemist of Copenhagen has discovered a brilliant yellow 

 matter for dyeing, in potatoe tops. The mode of obtaining it is, 

 by cutting the top when in flower, and bruising and pressing it 

 to extract the juice. Linen or woollen soaked in this liquor du- 

 ring forty-eight hours takes a fine, solid and permanent yellow 

 colour. ' If the cloth be afterwards plunged in a blue dye, it then 

 acquires a beautiful permanent green colour. 



PLUMBAGO. 



A few months ago a new mine of this valuable substance was 

 discovered in Glenstrathfarar, county of Inverness, in a schistose 

 rock close to the Farar. It crops out to an extent of not less 

 than fifty feet in five different seams, some of them from twelve 

 to fifteen inches in thickness. Several tons of it were raised last 

 summer. It seemed to improve much as the miners penetrated 

 deeper, and the seams to thicken and run into one. Only two 

 other mines of this substance are worked in Britain ; one near 

 Cumnock in Arvshire, the other at Borradale in Cumberland. 

 The produce of the latter is so valuable that the finer pieces sell 

 for two or three guineas a pound weight. 



LITHOVASA. 



This name is given to a new but useful article, made of a pe- 

 culiar kind of stone, in the form of vessels adapted to cool wine, 

 preserve butter, &c. They owe their properties to the power of 

 absorption and evaporation possessed by the stone ; and are su- 

 perior to earthenware articles applied to the same purposes, be- 

 ing entirely free from that clayey smell which belongs to unglazed 

 pottery. 



The wine coolers require only to be steeped for ten minutes in 

 told water, when they are fit to receive a decanter of wine. — The 

 <)Utter preservers steeped in the same manner are ready to receive 



a vessel 



