On Magneslo-Snlphate of Soda. 203 



water, althougli iucomplote, is so far valuable that it describes 

 the clotdie sulphate as o>ie salt, w'lile all otlier analytical writers 

 have stated tlie quantities of sulphate of soda and that of mag- 

 nesia separately. 



Perhaps the more accurate statement would be to estimate 

 first, how muoh of the triple salt exists, and then put dov/n the 

 quantity of that sulphate, whether of soda or magnesitt, which 

 is in' excess. 



In the analysis of the Kilburn water, both by Mr. Bliss and 

 Mr. Schineisser, the two sulphates are estimated as existing se- 

 parately; which cannot be correct, since in their mixed state 

 they possess new and peculiar properties. These gentlemen do 

 not exactly agree in the estimate of the two salts ; this difference 

 may however have been occasioned by one of them not making 

 his analysis at the same season of the year. 



As the subject is now in such very able hands, we shall probably 

 soon be favoured with Dr. Murray's analysis of this very useful 

 and commodious purgative salt ; I shall therefore forbear en- 

 tering u[)ou particulars at this time. Still, however, I must notice 

 that it is an article of which I have long had some knowledge, and 

 have witnessed its peculiar properties, having had, during the five 

 last years of my residence with Mr. Hume of Long Acre, very fre- 

 quent opportunities of observing many of its habits as a chemical 

 composition, and also of its efficacy as a medicine. That a mixture 

 of the sulphate of soda with that of magnesia requires less water 

 of crystallization, and that the compound salt proves more pur- 

 gative than either of the two constituents in the same propor- 

 tion, were, among other remarks, first noticed to me by Mr. 

 Hume. 1 know lie has long ago sold and recommended tliis 

 salt to many of the first professional men in London, and urged 

 its being admitted into the pharmacopoeia as a standard remedy. 



This salt, in the proportion of about one ounce or more to a 

 gallon of water, forms the best substitute for Cheltenham water. 

 There can be no chalybeate property obtained from the true 

 Chelterdiam water so as to be soiublt and useful in the salt re- 

 maining after evaporation, notwithstanding the plausible and re- 

 peated advertisements which endeavour to insinuate to the con- 

 trarv; for, the iron or, as it is poi)ularly termed, steel with which 

 nature has impregnated many mineral waters is nearly always 

 held in solution by carbunic odd; this compound is therefore in- 

 stantly destroyed by evaporation. But when the addition of a 

 chalybeate is recpiired, there are many obvious wavs of effecting 

 that purpose, of which no medic;;! man can be ignorant, and 

 such variation, when m.ade with judgement, must often produce 

 the happiest effects. I am, sir, 



Yours respectfully, 

 burton Creiccnt, Scjit. H, 1316. J. HealES, 



