On tlie Reaction of Sulphate of Magnesia and Bicarbonate of 

 Soda. By M. Planche. 



At is known that the bicarbonate of soda and the sulphate of 

 magnesia, in a state of aqueous solution, exercise no reciprocal 

 action in the cold, and that it is only when a certain quantity of 

 carbonic acid has been disengaged by heat, or, in other words, 

 when the alkaline bicarbonate has passed into the state of sub- 

 carbonate, that the sulphuric acid prevails over the soda, and 

 leaves the magnesia to the carbonic acid. But I have nowhere 

 seen it mentioned that the two salts mixed together, in a dry 

 state, and in the form of powder, react upon each other. This 

 must at least be the case with regard to their immediate and in- 

 stantaneous mixture, since in this state they dissolve in water 

 without affecting its transparency, and consequently without any 

 decomposition taking place, or at least any apparent decomposi- 

 tion. Presuming upon this property of the two salts, a physi- 

 cian prescribed several years ago to M. de Sommariva, a mixture 

 of powdered sulphate of magnesia, and saturated carbonate of 

 soda. He gave alternately either this mixture alone, or bicar- 

 bonate of soda. Being charged with the preparation of both 

 these medicines, for a journey of three months, which M. de 

 Sommariva made annually to Italy, I always had the precaution 

 of placing the mixture, in a very dry state, and divided into par- 

 cels in tin canisters, to preserve it from humidity. I used the 

 same precaution with regard to the carbonate of soda. I observ- 

 ed that the sulphate of magnesia was free of hydrochlorate. 



During three years M. de S., a man very careful of his health, 

 and besides a good observer, never perceived that cold water be* 

 came turbid when he dissolved the two salts together in it ; but 

 in 1822, having been obliged to prolong his journey beyond the 

 usual time, he laid up a store for a year. Toward the end of 

 the fifth month, M. de S. remarked that the same water which 

 he ordinarily used became slightly milky, and that the change, 

 which he rightly attributed, though without being able to ex- 

 plain the cause, to the alteration of the powder, went on increas- 

 ing as the time advanced. At length, by the seventh month. 



