1G4- Pi-0('('i'(liit(]i of the Boyal Soeii'tij. 



Colicn pirtoinhit, l)i'oke out in tlie house supplied w ith the water. In 

 this case, tlic water was by no means pure, as it was iound to con- 

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

 scarcely any other salt present except nmriates, which the author 

 had ascertaineil in his former researches not to prevent the action 

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



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

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

 the only remedy formerly thought of was substitution of iron- 

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

 the i^ater was left at rest in the pipe for four months, till a firm 

 crusi 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 27,000th of the salt. 



The author appended an analysis of the compound formed by the 

 action of distilled water on lead, Guyton-Morvcau and others con- 

 sidered it a liydrated 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 octahedron, and which is composed 

 of two equivalents of neutral carbonate, united with one equivalent 

 of hydrated oxide (2 PbO CO'-'-f PbO Aq). 



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

 drav>'n in a pi'actical point of vIcav, from his present and previous 

 inquiries as to the use of lead for conveying water : — 



1. Lead-pipes ought not to be used for the purpose of conveying 

 water, at least where the distance is considerable, without a careful 

 chemical examination of the water to be transmitted. 



2. The risk of a dangerous impregnation with lead is greatest in 

 the instance of the purest water*. 



3. Water, which tarnishes polished lead, when left at rest upon 

 it in a glass vessel for a few hours, cannot be safely transmitted 

 through lead-pipes without certain precautions. 



