On Antimonial Vermilion.

The Chemical Gazette 322, 15.3.1856

By E. Mathieu-Plessy.

The author has invented a process which furnishes antimonial vermilion of a beautiful colour, and which is sufficiently simple to be employed in its preparation on the large scale.

Hyposulphite of soda is best prepared by the action of sulphur upon sulphite of soda; it is not usually allowed to crystallize. The sulphite of soda must be in the neutral state to avoid the action of the sulphurous acid upon the hyposulphite. The sulphite of soda is most simply and cheaply prepared in the following manner, recommended by Camille Köchlin. In the upper part of a vessel, the bottom of which is broken out, a sieve containing large crystals of carbonate of soda is fixed. Into the lower part of the vessel projects a furnace-pipe bent at right angles, which is attached to a small clay furnace. Into this furnace sulphur is thrown by little and little, and burns into sulphurous acid, which passes through the tube into the vessel, and there acts upon the carbonate of soda. The combustion of the sulphur may be regulated as occasion requires through the door of the ſurnace; the draught is quite sufficient, and in the course of three or four days the crystals of carbonate of soda are acted upon to a considerable depth. The very friable sulphite of soda may be readily separated from the unaltered nucleus if any remains, and the latter may then be put back into the sieve. The sulphite of soda is dissolved in water so as to produce a solution of 25° B., and this is saturated whilst hot with crystallized carbonate of soda. When effervescence no longer occurs on the addition of this salt (which is the best criterion, as litmus-paper gives no satisfactory indications), or rather when the dilute sulphite furnishes a slight effervescence of carbonic acid on the addition of muriatic acid, flowers of sulphur are added, and the mixture is heated in an earthen vessel for three hours on the water-bath, stirring, and replacing the water that eva porates. When the fluid is cool, it is filtered and diluted until it shows 25° B.

Perchloride of antimony is prepared by heating powdered black sulphuret of antimony with commercial muriatic acid. When the evolution of sulphuretted hydrogen begins to diminish at a gentle heat, the mixture is boiled for a few minutes. On cooling, the clear liquid is decanted. To avoid inconvenience from the sulphuretted hydrogen gas evolved during the solution of the sulphuret of antimony, it may either be passed into a solution of soda, or allowed to pass through a tube drawn out to a point at the extremity, close to which the flame of a spirit-lamp is placed; by this the sulphuretted hydrogen is burnt, even when it is mixed with much aqueous vapour. The solution of chloride of antimony obtained is diluted with water to 25° B.

When the solutions of hyposulphite of soda and chloride of antimony are thus prepared, the antimonial vermilion is prepared in the following manner:–4 litres of solution of chloride of antimony and 6 litres of water are poured into a stoneware basin, and after these 10 litres of the solution of hyposulphite of soda. The precipitate which is produced by the water is rapidly dissolved by the hypo-sulphite of soda in the cold. The basin is now placed in a water bath, which is heated to boiling; in this the temperature of the mixture gradually rises. Towards 86°F, the precipitate begins to form; it is at first orange-yellow, but gradually becomes darker. The temperature is allowed to rise to 131°F., when the basin is removed from the water-bath, and the precipitate is allowed to settle, which takes place rapidly. The fluid is separated from the precipitate by decantation; the precipitate is washed first with water containing one-fifteenth of muriatic acid, and afterwards with common water, then collected on a filter and dried. In the moist state the antimonial vermilion has a shining red colour, but in drying it loses a little of its lustre. It was also produced in the cold, but the process described is more certain and furnishes a finer colour.

The author has analysed the antimonial vermilion thus prepared, and at the same time examined the amount of water in the ordina orange-red sulphuret of antimony (precipitated by sulphuretted hydrogen). 0.668 grm. of the latter lost 0.038 grm. in weight when heated to 892°F.; 0.808 grm. of antimonial vermilion showed a loss of 0.009 grm. when heated to the same temperature. The latter might be attributed entirely to hygroscopic water, and the antimonial vermilion may therefore contain no chemically-combined water. The loss of weight which the orange-red sulphuret of antimony undergoes shows, on the contrary, that this contains water chemi cally combined, and this loss of weight gives it the composition SbS₃+HO. The further analysis of the antimonial vermilion was effected by treating a weighed quantity of it with nitromuriatic acid containing an excess of nitric acid. A portion of sulphur remained undissolved, which, after tartaric acid had been mixed with the fluid, and the latter had been diluted with water, was separated, dried, and weighed. The fluid contained the remainder of the sulphur in the form of sulphuric acid, which was determined by precipitation with chloride of barium. The antimony was merely determined from the loss. The result of the analysis was, that the antimonial vermilion consists of 1.1 per cent of water, 267 per cent. of sulphur, and 72.2 per cent. of antimony. As the water is to be regarded as non-essential, it appears that the compound consists entirely of sulphur and antimony.

—Polytechn. Centralbl., 1855, p. 1451