Adulterations of Sulphate of Magnesia. 
9 
mixed with nitrate of silver, which, in solutions of corrosive 
sublimate, will produce a white precipitate, insoluble in nitric 
acid, but soluble in aqua ammonia. Or " a drop of nitrate of 
tin, when added to a solution of corrosive sublimate, will 
precipitate of a dark brown colour, the three millionth part 
of a grain." 
ADULTERATIONS OF SULPHATE OF MAGNESIA. 
Sulphate of magnesia is most frequently adulterated with 
fine crystals of sulphate of soda, sometimes with muriate of 
magnesia, and occasionally with sulphate of iron. 
To detect sulphate of soda, dissolve one hundred grains of 
the suspected salt in distilled water, and add an equal weight 
of sub-carbonate of soda ; boil this and wash and dry the pre- 
cipitate obtained, which, if the salt be genuine, will weigh 
exactly thirty-four grains ; if less than this it is impure ; or 
the solution of the pure salt will give no precipitate with car- 
bonate of potass. The presence of muriate of magnesia may 
be known by the disengagement of chlorine when sulphuric 
acid is added to the salt ; or by its deliquescence, when ex- 
posed to the atmosphere. On the contrary, if epsom salts be 
pure, on being exposed to the air they will effloresce. 
I have seen some specimens of the article contain sulphate 
of iron, which I detected with tincture of galls and also with 
ferrocyanate of potass. Epsom salts, adulterated with sul- 
phate of iron, may be completely purified by adding car- 
bonate of magnesia to the solution ; a double decomposition 
takes place, the sulphuric acid of the sulphate of iron unites 
with the magnesia and forms sulphate of magnesia, and the 
carbonic acid of the carbonate of magnesia combines with 
the iron and forms earbonate of iron, which is precipitated. 
I am informed that some experiments have been made by 
the New York Chemical Manufacturing Company with the 
magnesian earth called serpentine, which is very abundant 
at Hoboken, with the view of making epsom salts, but which 
Vol. I.— No. I. 2 
