30 COATING OF IRON OR STEEL — FORBES. 



ber until tlie desired depth of coating was obtained. This method 

 also requires considerable preparation in the way of suitably 

 arranged facilities for its execution. 



I now beg to explain a method which I have had occasion to 

 use, which I have not found suggested by any authority with 

 which I am acquainted, and which may have a field of adapta- 

 bility in cases where an expeditious or rough and ready way of 

 producing such a coating upon iron and steel articles is desirable. 

 The method consists in enclosing the articles in a sheet iron box, 

 imbedding them in some suitable supporting material which will 

 not absorb oxygen, say blacksmith's scale, or gravel, or sand, and 

 mixing with the contents of the Ijox some substance which will 

 give off oxygen when heated. 



After some consideration I conjectured that Black Oxide of 

 Manganese, MnOs would be a suitable agent, and upon experi- 

 menting was pleased to find my anticipation correct, and after a 

 few trials succeeded in obtaining results which for the desired 

 purpose seemed fairly satisfactory. We found that the thickness 

 of the coating may be increased to an appreciable degree ; the 

 colour is quite good and uniform, and the adherent qualities 

 generally satisfactory. 



We discovered that the quality of the peroxide of manganese 

 was important, and suffered disappointment in endeavoring to 

 use some that was not adapted to the purpose. It should be of 

 a good, deep black color, aad decidedly granular. That which 

 disappointed us was of a somewhat brown tinge, and dusty. 



It may be interesting to state, that after finding our plan to 

 succeed, we thougfht we would trv the mixingf of some other 

 agent with the Mn02, and so mixed a little chlorate of potash 

 with the oxide of manganese. The result was quite unsatisfac- 

 tory,— in some cases sticking to the surface, and in others causing 

 the resulting oxidation to be non-adherent, and dropping off* in 

 large plates as soon as handled. It is probable that the process 

 as we have hitherto practised it ina,y be improved, as we have 

 only made use of the same appliances, furnaces, etc., that we 

 have used for other purposes in connection with our business. 

 It is, however, in this readj^-to-hand feature that the chief utility 

 of the method probably consists. 



