614 TRANSACTIONS OF THE AMESICAN INSTITUTE. 



the iron. But the analysis showed there was scarcely a trace of foreign 

 metal there. The tubes of the condenser and copper pipes were all in per- 

 fect condition. Even at the joints, made tight by india rubber, hardened 

 by vulcanizing, there was hardly a speck of corrosion. 



A search was then made to ascertain whether the gluey deposit was pre- 

 sent that arises from the decomposition of tallow and oil used, and without 

 success. In case a fat acid might be the cause, pieces of chalk were put 

 into the boilers, and from time to time fresli pieces were added; carbonate 

 of soda was also mixed with the feed water in regular doses, but all to no 

 purpose; the action went on, getting worse and worse. The practical 

 knowledge thus acquired necessarily led him to the conclusion that the dis- 

 tilled water itself was the cause of the corrosion, instead of galvanic action 

 or any fatty acid. In reference to the question whether distilled water has 

 any particular action on metals, the chemist Berthier found that nodular 

 protuberances deposited on iron pipes containing distilled water, consisted 

 of twentj'-one per cent, of protoxide of iron, fifty-eight per cent of peroxide 

 of iron, five per cent, of carbonic acid, fourtetai and a-half per cent, of water, 

 and one and a-half per cent of silica. The iron pipes contained also a pul- 

 verulent substance, which could be produced at pleasure with distilled 

 •water, to which a trace of carbonate of soda and common salt had been 

 added, but not with the addition of caustic alkali. Mr. Ramsbottom stated 

 at the same meeting that he had found similar eflects in using peat water, 

 "which was almost as pure as distilled water. Both he and Mr. Markham 

 had found carbonate of lime would prevent corrosion. Mr. Gray thought 

 the corroding was due in locomotives to the brass tubes, used in England 

 in such engines, for on examining the pitted plates with a microscope, he 

 had found a minute speck of brass in the centre of many "pits." Mr. Rollo 

 did not concur in this opinion, if applied to boilers in connection with sur- 

 face-condensers; but thought it just possible that the fatty matter contained 

 in the grease had something to do with deteriorating the quality of the 

 water, and causing its corrosive action. 



At the conclusion of the reading of this abstract, Mr. Sewell restated 

 some of his views expressed at a former meeting. 



Dr. Parmelee inquired whether sulphuric acid was not employed in pre- 

 paring the lubricating compounds u.sed, and suggested that the presence of 

 a small quantity might originate this corrosion. 



Mr. Vedder stated that the acid was not used in preparing the tallow, 

 but it was largely in refining coal oils and petroleum. 



Mr. Griffin, a practical engineer, said he had found the tubes of two high- 

 pressure boilers, placed side by side, eaten away. One had iron pipes- lead- 

 ing to it, and the other copper. The tubes were corroded both above and 

 below the water line. This evidence bears strongly against the supposi- 

 tion that the cause is galvanic action. 



The further discussion showed that in the surface-condensing apparatus 

 and boilers used in this country, no serious effects have been observed 

 when the copper tubes of the condensers are tinned and a small quantity 

 of salt water is used in the boiler. 



After selecting the subject of " Iron" for the next discussion, the Asso- 

 ciation adjourned. 



