154 DR WILSON ON THE SOLUBILITY OF 
It seemed well worth while to seek for fluorine in one of these waters. I 
obtained accordingly from Mr CampBeLv’s brewery, a portion of the abundant 
deposit, consisting chiefly of sulphate and carbonate of lime, which collects with 
great rapidity in the boilers. It was treated with nitric acid, the dissolved portion 
poured off, neutralized with ammonia, and precipitated by nitrate of baryta. The 
precipitate, after being washed and dried, was warmed with Nordhausen sulphu- 
ric acid, in a lead basin; a square of waxed plate-glass, with characters traced 
through the wax, being laid as a cover overit. In this, as in all other experiments 
of the kind, a wall of wax was raised on the edges of the upper side of the glass, 
so as to retain a portion of water sufficient to keep the plate cool, and condense 
the hydrofluoric acid on it. This simple, but useful device, I borrowed from Dr 
Daupeny.* Three squares of glass were very distinctly, though not deeply, etched 
in this way. 
Fluorine, then, was present in this water; and the fact has an interesting 
relation to the circumstance pointed out to me by Mr Ross, that the well from 
which it was obtained is sunk through a bed of sandstone, containing much mica, 
a mineral in which Rost,t Turner, Grecory,t and other analysts, have found 
between 1 and 2 per cent. of fluorine. In reference to the corrosion of the brewery 
thermometers, however, I wish it to be distinctly understood, that I do not seek to 
refer the whole abrasion of the glass to the action of a fluoride dissolved in the 
water in which they are immersed. ‘The well-known experiments of LavoisrIER, 
made in the end of last century, proved that even distilled water, if long boiled 
upon glass, can corrode it. Every chemist is familiar with the rapid action of 
solutions of the fixed alkalis, and of phosphate of soda on flint-glass. The in- 
ferior kinds of bottle-glass, especially when containing too little silica and excess 
of lime, have been shewn by Farapay|| and Warrineton to suffer corrosion by 
the action of wine, and of diluted hydrochloric, sulphuric, and tartaric acids; 
and it would be rash to suppose that these are the only re-agents that can act 
upon. artificial silicates, especially upon those which contain excess of basic 
oxides. 
On the other hand, it is impossible not to connect the fact that the thermo- 
meters are corroded, with the circumstance that the water which occasions this 
corrosion contains fluoride of calcium. The other constituents of the brewery 
water are chloride of calcium and sodium, sulphate of lime and of soda, carbo- 
nate of lime and of magnesia, silica and organic matter; no one of which is known 
to have any action on glass. 
In connection with this fact I may mention, that Mr Srevenson finds the 
thermometers used in the breweries in the valley of the Cowgate much more 
* Chemical Society’s Memoirs, vol. ii., p. 101. + Poaernporr’s Annalen, vol. i., p. 80. 
{ Brewsrer’s Journal of Science. || Chemical Society’s Memoirs, vol. ii., p. 247. 
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