ACTION OF WATER ON IRON. 291 



mens furnished us, the iron, which is all wrought, (and its ap- 

 plication to the more carbonaceous cast irons must be more 

 difficult,) is zincked or, if the expression may be used, tinned 

 with zinc ; the coating is excessively thin, and from its peculiar 

 greasy feel, leads to the presumption that it has been slightly 

 amalgamated also. 



89. I was enabled to detach from one spot a few grains of 

 zinc, which, on examination, appeared to be as pure as it is 

 usually found in commerce. I expected to have found it alloyed 

 with lead ; of this it contains a trace, and a good deal of iron, 

 probably taken up in part from the bar. No mercury could be 

 detected in it. 



90. A very few minutes are sufficient to dissolve oif the whole 

 of the zinc from the surface of the iron when immersed in hy- 

 drochloric acid, diluted with 40 volumes of water. 



91. Oxide of zinc is rapidly deposited in sea water or a solu- 

 tion of common salt, when acting on it. 



92. When a bar of the zincked iron is placed in hydrochloric 

 acid, diluted with 20 volumes of water, the zinc having been 

 completely removed by the file from one half of its surface, hy- 

 di'ogen is given off both from the zinc and iron surfaces from 

 the first moment ; and after the whole of the zinc is dissolved, 

 this gas is much more copiously evolved from the surface that 

 had been zincked, than from that from which it was filed off. 

 This circumstance appears to be connected with the strength of 

 the acid ; it does not occur in that which is very dilute. 



93. There can be no doubt of the power of this combination 

 to protect iron for a time, or while the thin coat of zinc lasts 

 perhaps, and in some practical points of view it would seem to 

 offer advantages over zinc protectors, as proposed being ap- 

 plied by Edmund Davy. But it seems to be forgotten by the 

 advocates of this attenuated application of the preserving metal, 

 that for every particle of iron protected, an equivalent of zinc 

 must be destroyed, and that hence, unless a sufficient mass of 

 the electro- positive metal is provided to allow for degradation, 

 its efficacy must soon be null. 



94. It is not intended, however, to pronounce any decisive 

 opinion as to the advantages or disadvantages of this peculiar 

 mode of applying zinc protectors until we have had time to make 

 other and careful experiments upon it; meanwhile, in justice 

 to my friend Professor Edmund Davj^, I must remark upon 

 the arrogation of original discovery to M. Sorel, the patentee 

 of this process, which some of the French scientific journals 

 make. It does seem strange how any pretension to originality 

 of discovery can be now set up on this score, after the previous 



