250 TOIVERS AND TANKS FOR WATER-WORKS. 



From the history of the Peoria stand-pipe, it having been 

 noted that the specifications called both for iron and steel as 

 structural materials and desiring to ascertain whether galvanic 

 or battery action might not have been the result of the iron and 

 steel in contact in the presence of moisture, the author wrote 

 Mr. Maury, receiving a reply in which he stated that he did 

 not think anything but steel plate had been used in the con- 

 struction of the stand-pipe, except the rivets, and possibly the 

 ladder and some connections; that careful investigations 

 looking for battery action were made, but this action had not 

 been substantiated. 



Cleaning the Metal. It having been shown and demon- 

 strated that it is of prime necessity to prevent the commence- 

 ment of the rusting process in its incipiency, and that the first 

 consideration is to provide for the thorough cleaning of the 

 metal before an attempt is made to give it a protective cover- 

 ing, it is in order to discuss the methods employed for this 

 process of cleaning or preparation for painting. 



For this purpose there are three processes in vogue and in 

 general use. One is by "pickling"; another by the use of 

 the sand-blast, and a third and more general method is by 

 scraping and cleaning with wire brushes. 



The pickling process consists in the submersion of the 

 plate or shape in a bath of hydrochloric or sulphuric acid for 

 a period of one-half to twenty-four hours, and afterwards 

 neutralizing the acid by the use of lime, the lime then being 

 cleaned off. The proportions of acid to water range from 10 

 to 19 parts of water to I of acid, the latter being the formula 

 adopted by the British Admiralty. Such a method of clean- 

 ing plates, while reasonably economical and convenient, and 

 fully effective when carefully performed, is open to the objec- 

 tion that any carelessness upon the part of the workmen is sure 

 to produce results which are worse than the proposed cure. 

 The second method of cleaning metallic surfaces is a mechani- 



