. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . The solutionis then concentrated by evaporation, an excess of carbonate of soda added, and it is evaporated todryness, to decompose the ammoniacal salts, and drive off the ammonia as carbonate ; it is thentreated with water, which leaves the magnesia in the state of insoluble carbonate. In the analysis just described, the proportions of all the various components of the glass havebeen ascertained successively, with the exception of those of the alkalies, wh
. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . The solutionis then concentrated by evaporation, an excess of carbonate of soda added, and it is evaporated todryness, to decompose the ammoniacal salts, and drive off the ammonia as carbonate ; it is thentreated with water, which leaves the magnesia in the state of insoluble carbonate. In the analysis just described, the proportions of all the various components of the glass havebeen ascertained successively, with the exception of those of the alkalies, which must be found bya particular process. The glass is first dissolved in fluohydric acid. As this acid is difficult of pre-servation, it is better to prepare it freshly for each analysis, which is done in the following manner ;—Into a small platinum retort, Fig. 3299, made of two pieces, very finely powdered fluor-spar isintroduced and sulphuric acid added ; on the other hand, 5 grammes of glass in impalpable powderare placed in a large platinum crucible, with a certain quantity of water, and covered with a sheet GOLD. 1689 of platinum pierced with two openings. The neck of the platinum retort passes through one ofthose openings ; the other, much smaller, is traversed by a platinum wire, flattened into a spoon atits end, and used for stirring thematerial in the crucible. Ongently heating the retort thefluohydric acid dissolves in thewater of the crucible, attacksthe vitreous matter, and a largequantity of fluoride of silicium isdisengaged. The material isstirred from time to time withthe platinum spoon, and whenthe glass is entirely dissolved,the crucible is gently heated, todrive ofí the excess of acid andevaporate the water; sulphuricacid is then poured upon the re-sidue, completely to expel thefluohydric acid and convert allthe oxides into sulphates. Whenthe greater part of the sulphuricacid has been driven off by heat,the substance is treated withwater, which lea
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Keywords: ., bookcentury1800, bookdecade1870, bookidsp, booksubjectengineering
