404 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



have the value of steeh When the iron fii'st runs down from the 

 ore, in a blast furnace, it contains its maximum of carbon. This 

 is expelled in the puddling process, and other impurities are 

 forced out in the tiltii]g and rolling. If the puddling and tilting 

 are interrupted at the point where the iron contains just the 

 right proportion of carbon, it is called puddled steel. The 

 question is which is the cheapest and best in the end, to purify 

 the iron completely, and then to retrace the step and restore the 

 carbon, or to arrest the decarbonization at the proper point. 



Dr. Vanderweyde considered it a settled matter that nitrogen 

 is one of the elements of steel. There seems to be a general law 

 that an alloy will always be more fusible than the pure substance. 

 Tin and lead alone are neither as fusible as a compound of tin 

 and lead. So iron and carbon are more fusible than iron alone. 

 And if other substances are added, it will be still more fusible. 

 If silicium, sulphur, phosphorus, are added, they injure the 

 quality of the iron and make it brittle. But other substaiices 

 may be put in which will improve its quality. A small quantity 

 of titanium put into cast iron, if there are no other impurities 

 present, will make it almost as good as steel. The reason why 

 nitrogen has not been found by chemists is that it is a very difiB- 

 cult substance to detect in consequence of its lack of positive 

 qualities. It does not readily show itself or enter into combina- 

 tions. All the compounds used to make steel upon the surface 

 of iron contain nitrogen. For instance, the blacksmith uses the 

 yellow prussiate of potash to harden the surface ; and it will 

 make the surface so hard that the file will not attack it. In case- 

 hardening, scraps of horn and various other nitrogenous substan- 

 ces are used. It is often remarked that a chemist does not know 

 the difference between cast iron and steel, but a blacksmith does. 

 But the blacksmith has not the monopoly of the process of 

 hardening; the chemist may use all the means which the black- 

 smith uses to determine the difference. 



Mr. Dibben. — I can find cast iron that neither the chemist nor 

 the blacksmitb can tell from cast steel. Cast iron and steel are 

 the same thing, only that cast iron contains more foreign mat- 

 ters than steel. Cast steel can be produced with so large a 

 quantity of carbon that it will have the same appearance and 

 properties as cast iron. If we take a good iron ore we may pro- 

 duce samples of puddled steel equal to any specimens ever made 

 in the usual manner. It is cast iron only, that it has been ham- 



