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Updated: June 21, 2025
The weight of silica is 0.6460 gram. This is fused with 4 grams of sodium carbonate. How many grams of the carbonate actually combined with the silica in fusion, and what was the loss in weight due to carbon dioxide during the fusion? !Answers!: 1.135 grams; 0.4715 gram. A mixture of barium oxide and calcium oxide weighing 2.2120 grams is transformed into mixed sulphates, weighing 5.023 grams.
We select, then, a compound which is a chloride, and a chloride of a metal which forms an insoluble combination with sulphuric acid chloride of barium, say.
One hundred cubic centimeters of the solution, when titrated with 0.1062 N hydrochloric acid, using methyl orange as an indicator, requires 38.60 cc. for complete neutralization. Barium chloride in excess is added to a second portion of 100 cc. of the solution, which is diluted to exactly 250 cc., allowed to stand and filtered.
The second half of the filtrate is used for determining the small quantity of sulphate of lime still contained in the hydrochlorate solution. By adding chloride of barium solution the sulphuric acid is bound to the barytes and sulphate of baryta separates as white precipitate. This is separated by filtering, washed, dried and weighed in the customary manner.
Everything must be registered. Will the medium be able to impress a photographic plate? Will she be able to illuminate a screen treated with platino-cyanide of barium? Will she be able to discharge a gold-leaf electroscope without touching it?" And so we travelled on the wings of imagination, always having before us the plummet of the strictest scientific methods."
The one fault or shortcoming of the plain argentic paper is the dullness of the surface when dry, and this certainly makes it unsuitable for small work, such as the rapid production of cartes or proofs from negatives wanted in a hurry; the tone of an argentic print is also spoken of sometimes as being objectionable; but my impression is, that it is not so much the tone as the want of brilliancy that is the fault there, and if once the public were accustomed to the tones of argentine paper, they might possibly like them twice as well as the purples and browns with which they are familiar, provided they had the depth and gloss of a silver print; and some time ago, acting on a suggestion made by the editor of the Photographic News, I set about trying to produce this result by enameling the paper with a barium emulsion previous to coating it with the gelatinous bromide of silver.
This case affords one of the best illustrations of the effect of an excess of a precipitant in decreasing the solubility of a precipitate. It should be borne in mind that the quantity of barium sulphate in this !saturated solution is a constant quantity! for the existing conditions.
!Standard Alkali Solutions! may be prepared from sodium or potassium hydroxide, sodium carbonate, barium hydroxide, or ammonia.
If sulphuric acid is present it must be separated by treating the solution of the compound with barium chloride and filtering. A nearly neutral solution is prepared in water or hydrochloric acid and placed in a flask. Here it is treated with chlorine by passing a current of that gas through it as long as it causes a precipitate and for some time afterward.
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