HYPO-SULPHITE OF SODA. 
223 
ART. LII DESCRIPTION OF A VERY SIMPLE PROCESS 
FOR PREPARING HYPO-SULPHITE OF SODA. 
By M. Walchner. 
Having received an order for several pounds of this salt, 
which has of late come into very extensive use, both for 
preparing, as well as for gilding, Dauguerreotype portraits, 
I was induced to search for a more simple method of pre- 
paring it than that generally followed. I found that this 
salt may be obtained in a very short time, and in great quan- 
tity, by the following simple process : — Pure crystallized 
carbonate of soda is dried as much as possible, and reduced 
to a fine powder; one pound of it is then mixed with ten oz.of 
flowers of sulphur, and the mixture heated in a glass or por- 
celain dish, gradually, until the sulphur melts. The mass, 
which cakes together, is kept at this temperature, and is di- 
vided, stirred, and mixed, in order that each part may be 
brought into contact with the atmosphere. The sulphuret 
of sodium formed, passes, under these circumstances, by the 
absorption of oxygen from the atmosphere, with a slight in- 
candescence, gradually into sulphite of soda. It is dissolved 
in water ; filtered ; the liquid immediately boiled with 
flowers of sulphur; the filtered, nearly colorless, strongly 
concentrated liquid affords hypo-sulphite of soda, in very 
pure and beautiful crystals, and in large quantity. 
When the mixture is heated too quickly, some sulphur is 
easily burnt; there then remains a portion of undecomposed 
carbonate of soda, which contaminates the hypo-sulphite in 
the first crystallization, but which may very readily be se- 
parated from it. 
•/Inn. der Chem. und Pharm. } for May, and Chem. Gaz. 
