359 



in a lead-pipe f'lviii a distance of three quarters of a mile, was found 

 to act so powerfully on the lead, that in a short time the cistern in 

 which the water was collected became covered with loose carbonate of 

 lead, and the metal could easily be detected in the state of oxide dis- 

 solved in the water. In this case, the action was found to depend 

 on the spring being of extraordinary purity, its total saline ingre- 

 dients being only a 22,000th part. In the other instance, water 

 conveyed half a mile in a lead-pipe, was impregnated exactly in the 

 same way, and with the very same phenomena, — but with the addi- 

 tional circumstance, that, in consequence of the impregnation not 

 having been detected in time, as in the previous case, the disease, 

 Colica pictonwn, broke out in the house supplied with the water. In 

 this case, the water was by no means pure, as it was found to con- 

 tain no less than a 4,500th part of saline matter. But there was 

 scarcely any other salt present except muriates, which the author 

 had ascertained in his former researches not to prevent the action 

 of water on lead, unless present in much larger quantity. 



He next proceeded to explain in what manner the action of the 

 •water was put an end to in both these cases. In similar instances, 

 the only remedy formerly thought of was the substitution of iron- 

 pipes. In the former of the two cases which fell under his notice, 

 the water was left at rest in the pipe for four months, till a firm 

 crust of mixed carbonate and sulphate of lead had crystallized on the 

 lead ; after which no farther action took place. In the latter in- 

 stance, the same end was attained by keeping the pipe full of a solu- 

 tion of phosphate of soda, consisting of a 27,000th of the salt. 



The author appended an analysis of the compound formed by the 

 action of distilled water on lead. Guyton-Morveau and others 

 considered it a hydrated oxide ; the author himself, in 1829, thought 

 it a neutral carbonate; and, in 1834, Captain Yorke first considered 

 it a hydrated oxide, and eventually concluded from his analyses, 

 that it is an irregular mixture of hydrated oxide and carbonate of 

 lead. The author finds that the product is a hydrated oxide, when 

 the action goes on without the access of carbonic acid; but that, 

 when the action proceeds in the usual way, under exposure to the 

 atmosphere, the product is a crystalline body, of which the primi- 

 tive form seems to be the regular octahedre, and which is composed 

 of two equivalents of neutral carbonate, united with one equivalent 

 of hydrated oxide (2 PbO C0» + PbO Aq), 



He then stated the following to be the general conclusions to be 



