270 PROFESSOR CHRISTISON ON THE ACTION OF WATER UPON LEAD. 



The architect, under whose directions the water had been introduced into the 

 house, was slow to believe that the housekeeper really suffered from the effects of 

 lead, or that the water was impregnated with this metal. Even the condition of 

 the principal cistern, which was found in precisely the same state as at Dalswin- 

 ton, did not open his eyes altogether to the truth, and indeed rather impressed 

 him with the notion that negligence in cleaning the cistern was the source of any 

 mischief that might actually have arisen. This was not surprising. For it was 

 plausibly argued, that such accidents had not been observed in other places, and 

 more especially at Aberdeen, where lead is prevalently used for conducting water ; 

 and the architect was probably unacquainted with the scientific details of the sub- 

 ject, as they have been hitherto little dwelt upon except in works on Toxicology. 



It has been just stated, that the spring was purchased as one of great purity, 

 represented from actual analysis to " contain but a very small quantity of solids." 

 I therefore inferred, that, like the water of Dalswinton, it was too pure for the 

 preventive power of the usual neutral salts of springs to be efficaciously exerted. 

 Being anxious, however, to fix positively the circumstances connected with so 

 remarkable an instance of the action of a natural water on lead, I obtained some 

 of the water for examination. It was transmitted by Mr JOHNSTON with all due 

 care to ensure its purity. The result is, that, although by no means the sort of 

 water it was alleged to be, the circumstances of the case come precisely under the 

 general principles established by me in 1829. 



The water is clear, colourless, and without taste. Polished lead immersed in 

 it becomes tarnished in a few hours, but undergoes no farther change in fourteen 

 days. Twenty thousand grains evaporated to dryness left a residuum, which, after 

 exposure to a low red heat, weighed 4.482 grains, indicating a 4460th of solids. 

 Hence the water is far from being a pure spring- water : It is not more so than 

 that of many streams in the Scottish Lowlands. It contains, in fact, so large a 

 proportion of salts, that, if these were of the ordinary kind, lead Avould scarcely 

 be acted on by it at all. But its ingredients are chiefly the least energetic in pre- 

 ventive power of all the salts usually found in terrestrial waters. Oxalate of am- 

 monia has at first no effect, but slowly causes a slight haziness ; which in some 

 hours gives place to a scanty white precipitate, indicating the presence of a mere 

 trace of lime. Phosphate of ammonia has no effect even after twenty-four hours ; 

 but when the water is much concentrated, this test occasions a crystalline pre- 

 cipitate, proving the existence of a minute trace of magnesia. Nitrate of baryta 

 produces slowly a very scanty precipitate. As neither this precipitate, nor the 

 saline residuum obtained by evaporating the water to dryness, presents any effer- 

 vescence with diluted nitric acid, the water does not contain any carbonate. The 

 barytic precipitate from 4375 grains of water weighed 0.218 of a grain, and there- 

 fore corresponded with the small proportion of only a 32,000th of some sulphate, 

 either sulphate of soda or probably sulphate of lime. Nitrate of silver, however, 



