An analysis of plate glass / by J.S. Brazier.

  • Brazier, James S. (James Smith)
Date:
[1850?]
Catalogue details

Licence: Public Domain Mark

Credit: An analysis of plate glass / by J.S. Brazier. Source: Wellcome Collection.

    2/4 (page 22)
    The specific gravity of these specimens of glass is as follows :— British Plate Glass 2‘319 London Thames Plate Glass - - - - 2’242 London and Manchester Plate Glass - - 2 408 A qualitative examination showed the presence of silicic acid, potash, soda, sesquioxide of iron, alumina, lime, and in one case traces of manganese. The silicic acid was determined in the usual manner, by fusion with pure carbonate of potash. The sesquioxide of iron, the alumina, and the lime, were afterwards precipitated from the hydro-chloric filtrate. To determine the alkalies, the glasses were decomposed by means of hydrofluoric acid, in an apparatus recommended by Brunner,* which consists of a leaden capsula with a flat bottom about six inches in diameter and four inches high, in the centre of which is placed a small leaden ring about an inch and a half high, which serves as a support for. a platinum dish. The leaden capsula has a cover fitting perfectly tight. To set the apparatus in action, it is necessary to cover the bot¬ tom of the capsula with a layer of pulverised fluorspar about half an inch in thickness, and to pour upon it some sulphuric acid, sufficient to form a thick paste. A weighed portion of the finely pow'dered glass, after being put in the platinum dish, is covered with water, and placed on the leaden ring. The whole is then kept at a gentle heat either on a sand bath, or by means of a spirit-lamp. By a few preliminary experiments, the action on the glass was found to be exceedingly slow, when covered merely with water ; it was then suggested to me by Dr. Hofmann to try, instead of water, a strong solution of ammonia ; it was found that, the hydrofluoric acid being much more rapidly absorbed by this latter agent, the decompo¬ sition was facilitated in a remarkable manner. The first of the two following tables shows the amount of sub¬ stance employed ; the results obtained are exhibited in Table II. I. II, III. British London Thames London & Manchester Plate Glass. Plate Glass. Plate Glass. 1 2 1 grm. 2 grm. Plate Glass. 1 2 grm. grm. grm. grm. 3429 1-1750 1-1579 1-1906 1.0508 1.1095 2-1500 1-4200 1-6800 1-0200 2-0700 Poggendorff’s Annalen, XL1\ ., page 134