Dr. Scudafnore on Mineral Waters, 309 



that the addition of phosphate of soda may throW^own phos- 

 phate of hme, as well as the phosphate of ammonia and magnesia. 

 Whether any difficulty occurred to Dr. Scudaraore on this ac- 

 count in determining the quantity of magnesia, he does not 

 mention, but I think it probable; for the method by which he 

 determined the quantity of magnesia was that of decomposing 

 the muriate obtained from the alcoholic solution, by means of 

 carbonate of soda, then adding sulphuric acid to the carbonate 

 of magnesia, suffering the sulphate of magnesia to crystallize by 

 slow evaporation, and again decomposing the sulphate by car- 

 bonate of soda, and decomposing *the carbonate of magnesia by 

 heat, and then calculating the quantity of muriate of magiiesia 

 which it would yield. 



From some late experiments I am induced to beheve 

 that lime water is not only the best test (with certain precau^ 

 tions), but also the most eligible substance for obtaining the 

 magnesia from a mineral water. 



Supposing no alkaline carbonate nor any alumina to exist in 

 a water, and that the oxide of iron has been separated, hme 

 water will discover an extremely minute portion of magnesia, 

 when the saline contents of the water have been obtained 

 by evaporation and redissolved in distilled water : Thus, I find 

 that the twelfth part of a grain of magnesia, and even a much 

 smaller quantity, may be readily shown to exist in a pint of 

 water, and is easily precipitated from combination with an acid 

 by lime water. The only inconvenience to be avoided, is the 

 possibility that the excess of lime water used, may deposit 

 carbonate, if the air be not carefully excluded during the filtering 

 and washing of the precipitate. 



It is, however, but due to Dr. Scudamore to state that I have 

 found magnesia actually existing in this water, but which I did 

 not beheve to be the case until I read his work, and even when 

 1 had, I doubted as to the accuracy of his statement. My sus- 

 picions of the Doctor's inaccuracy were indeed strengthened by 

 an experiment w^hich he relates, and v/hich I had tried with si- 

 milar results, viz. that lime water occasions no precipitate iii 

 Buxton water which had been boiled : this experiment induced 

 me to believe that the water contained no magnesia; but, on 

 evaporating a portion to dryness, and redissolving the saline re- 

 siduum in water, a precipitate of magnesia actually occurred. It 

 will not be surprising that lime water did not indicate the mag- 

 nesia in the water without concentration, when it is stated that 

 the whole quantity which a gallon contains amounts to only 

 about 0*16 of a grain. I have considered this part of the sub- 

 ject merely with a view of determining the best methods of 

 detecting the presence of magnesia ; for I will hazard the 

 opinion, that in a medicinal point of view, the 0-l6 of a grain 

 of magnesia, however combined, cannot possess any very ex- 

 tensive influence when dissolved in a gallon of water. The 



