Hyposulphite of lime

Hyposulphite of lead PbS203.H20 Lead hydrosulphtte lead thlosulphiie Hyposulphite of lime 4246... 

In the process which I have followed, the vermilion of antimony is obtained by the reaction of the chloride of this metal upon a dilute solution of hyposulphite of lime and the mother-liquors are used several times, and are thrown away only after they contain too great a proportion of chloride of calcium. 

After a series of experiments (employment of leaden vessels, heating stoneware vessels in sand and pitch baths, etc.), I found that it was much better to roast the sulphide of antimony at a moderate temperature in contact with air and steam. The greater part of the sulphide is converted into oxide of antimony, and the sulphurous acid produced in the manufacture of the hyposulphite of lime. The oxide of antimony is then easily dissolved in commercial hydrochloric acid. 

Preparation of the Hyposulphite of Lime.—This salt is cheaply prepared by the action of sulphurous acid upon the sulphide or poly-sulphide of calcium, or the oxysulphide. The sulphurous acid is produced by burning brimstone or roasting pyrites or sulphide of antimony. 

Sulphurous acid, in its reaction upon the sulphide and oxysulphide of calcium, sets sulphur free and forms a sulphite of lime, which, in the presence of sulphur and undecomposed sulphide, is soon transformed into hyposulphite of lime. The reaction is aided by the elevation of temperature which takes place in the apparatus. 

After settling for some time, the clear liquid is decanted, and forms a solution of nearly pure hyposulphite of lime. The same vessel is subsequently used for neutralising the liquors obtained during the process of manufacture. 

Preparation of Vermilion of Antimony.—The red sulphide of antimony is prepared with the above solutions of chloride of antimony and of hyposulphite of lime. 

When the pressure of the boilers has reached two or three atmospheres, the tanks are filled with the solution of hyposulphite of lime up to seven-eighths of their height. We then pour the solution of chloride and antimony into the first tank, 2 or 3 litres at a time. There is formed a white precipitate which is rapidly dissolved at the beginning but when solution becomes slow, even when the liquor is stirred, the addition of chloride of antimony is discontinued, because there should always be a certain excess of hyposulphite of lime. 

The clear and limpid liquor, which smells strongly of sulphurous acid, is decanted through holes bored in the tank at di erent heights, and is conducted by means of leaden pipes or wooden troughs into a large quantity of sulphide and oxysulphide of calcium. The sulphurous liquor regenerates a certain proportion of hyposulphite of lime. 

We should carefully avoid, in this regeneration of the hyposulphite of lime, leaving in an excess of sulphide of calcium, which will impair the coloration of the vermilion by causing the formation of the ordinaiy orange-yellow sulphide of antimony. Therefore, if the solution of hyposulphite of lime be ydlow and alkaline, a liquor charged with sulphurous acid should be added, until complete neutralisation of the alkaline reaction. 

This solution of hyposulphite of lime, like the first, is employed in the preparation of a new quantity of vermilion of antimony. The mother-liquors, charged with sulphurous acid, are again neutralised in the large reservoir by a new proportion of sulphide and oxy-sulphide of calcium, and so on, until the liquors become so much loaded with chloride of calcium that it becomes necessary to throw them away, or to reserve them for some other purpose. But this take place only after twenty or thirty operations. 

It is even possible to save the sulphurous acid in these exhausted mother-liquors, by saturating them with a milk of lime. This produces a precipitate of oxide of iron and of sulphite of lime, and leaves chloride of calcium only in the mother-liquors. The precipitate, mixed with sulphide of calcium, is transformed by sulphurous acid into the hyposulphites of lime and iron. And if the proportion of iron be too great, it may be precipitated by a slight excess of milk of lime. 

It is a nearly white powder, provided no excess of charcoal is present, and is very sparingly soluble in water. When it has been exposed to the sun s rays, it shines in the dark, and is called Canton s phosphorus. When water, lime, and sulphur are boiled together, there is formed a yellow or orange solution containing hyposulphite of lime and persulphuret of calcium. This liquid, acted on by hydrochloric acid, yields persul-phuretted hydrogen. When sulphur and lime are melted together, there is formed a mixture of sulphate of lime and sulphuret of calcium. 

If, during the oxidation of the sulphide of antimony, there is produced a certain propoiiaon of antimonious acid, but slightly soluble in HCl, it may be saved by collecting the residues from the treatment with hydrochloric acid, and washing them with chloride of calcium or hyposulphite of lime, which dissolves the adherent Bulletin de la Soditi industrielle de Mulhouse, vol. zz. pp. 879 el seq. 

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