30 An Analysis of the Cheltenham Salts. [Jax. 



or its carbonate. I did not determine which, because the dose 

 in which it is exhibited scarcely amounts to -jV-h °f a grain. 



This salt loses 44 per cent, by being heated ; and the remain- 

 ins; 56 parts consist principally of- Epsom salt mixed with about 

 T \. th part of a grain of magnesia, or its carbonate, and a small 

 portion of muriate of magnesia, or of common salt ; I have not 

 examined, nor does it matter, which. 



The last preparation to be noticed is called by Mr. Thompson 

 " Murio-sulphate of magnesia and iron."' Of the existence of any 

 compound to which this name is applicable, I am as ignorant as of 

 the subsulphate of magnesia asserted to exist in the last-described 

 salt ; nor is it indeed clear what is intended to be conveyed by 

 this appellation ; it may mean either a binary compound of mu- 

 riate of magnesia and sulphate of iron ; or a quaternary one of 

 muriatic acid, sulphuric acid, magnesia, and iron ; but the salt 

 in question is neither of them. 



One hundred grains heated to redness lost 37-5 gr. A similar 

 quantity put into water left 01 of a grain undissolved, which 

 ■was evidently peroxide of iron. Tincture of galls added to the 

 solution did not give any evidence of its containing oxide of 

 iron ; and from two separate solutions of 100 grains of the salt 

 I obtained, by nitrate of barytes, 121 grains of sulphate of 

 barytes ; and by nitrate of silver, 3 - 3 grains of horn silver. Now 

 these quantities of sulphate of barytes and of horn silver indicate 

 about 61 of sulphate of magnesia and 1*4 of muriate of mag- 

 nesia. 



This salt, then, described by Mr. Thompson as " murio-sul- 

 phate of magnesia and iron," consists of about 



Peroxide of iron 0" 1 gr. 



Sulphate of magnesia 61* 



Muriate of magnesia I'4 



Water 37-5 



100-0 

 In plain English, this salt consists of Epsom salt deprived of 

 part of its water of crystallization, discoloured by a little rust of 

 iron, and liable to become rather damp by exposure to the air, 

 on account of the deliquescence of the muriate of magnesia 

 which it contains. 



It has been justly observed of these preparations " that not 

 one of them is similar to the w T ater which is drank at the Spa." 

 In order to obviate this difficulty, Mr. Thompson prepared the 

 " original combined Cheltenham salts," by evaporating the 

 w-aters to diyness. I shall presently state my reasons for be- 

 lieving that this process cannot remedy the defect described ; 

 and in corroboration of my opinion 1 I may remark, that Mr. 

 Thompson has allowed that " the medical gentlemen who gave 

 it a trial [the original combined Cheltenham salt] did not make a 

 favourable report of it." It is presumed that the tonic eifect of 



