104 Scientific Intelligence. 



portion of the clilorid is supposed to decompose during the experiment, 

 through the humidity of the air; and in this way M. Pierre accounts 

 for the variation in the above results. Believing that the first three 

 results are most correct, he adopts the number 314*69 (or on the hy- 

 drogen scale, 25*13) for the equivalent. 



7. On the compounds of Iron with Carbon ; by M. Karsten, (Bericht 

 Berlin Akad., Nov. 5, 1846; Chem. Gaz., March, 1847.)— The deter- 

 mination of the amount of carbon in the different kinds of bar iron, 

 steel and pig iron, are still variable and uncertain, partly owing to the 

 estimation of the amount of carbon being very tedious if not difficult, 

 and partly because the limits between bar iron and steel, as well as be- 

 tween steel and pig iron, are wholly undetermined, and are merely as- 

 sumed conventionally from certain physical properties of the product. 

 Combinations in definite proportions between iron and carbon are not 

 to be met with in the carburets of iron ; for the union of these two 

 substances takes place in indefinite proportions, uninterruptedly, from 

 to the maximum amount of carbon, which is about 5*93 per cent. 

 The classification of the carburets of iron in three divisions, bar iron, 

 steel, and pig iron, is consequently not necessary, i. e., not required, by 

 the combining proportions, but wholly arbitrary. 



To determine the amount of carbon, the best methods of separating 

 the carbon from iron were employed ; but in order to ascertain the de- 

 gree of trust-worthiness belonging to each, white pig iron, with a bright 

 metallic surface, smelted with charcoal from sparry iron ore at the 

 Sayner works near Bendorf on the Rhine, was submitted to experiment. 

 This pig iron contains no uncombined carbon (graphite), or at least 

 but mere traces ; and the amount of combined carbon approaches 

 closely to the maximum amount which iron is capable of taking up. 



The amount of carbon of this pig iron was found, by different meth- 

 ods of analysis, as follows : 



Per cent 



By elementary analysis with oxyd of copper, the carbon be- 

 ing calculated from the carbonic acid gas, - - 42835 



5-7016 

 5-6987 



By elementary analysis with chlorate of potash and chro- 

 mate of lead, 



2d experiment, 



By decomposition of chlorid of copper, - - - 5*5523 



2d experiment, --.-.. 5*6978 

 By decomposition of perchlorid of iron 



1. Experiment with sublimed chlorid of iron, - 5*4232 



2. With perchlorid prepared in the moist way, 5*2867 

 By decomposition of chlorid of silver, ... 5*6056 



2d experiment, 



5*7234 



As all bar iron contains more or less carbon, some decision should be 

 made as to the limits up to which it should be called bar iron, and 

 below which steel. If the limits are fixed by calling that bar iron 

 steel which becomes so hard by cooling in water after having been 

 hardened that it gives sparks with quartz, this effect occurs only when 

 the iron has taken up 0*5 of carbon. Iron which is perfectly free from 

 foreign ingredients may even combine with 0-65 per cent, of carbon 

 before attaining the above degree of hardness. The purer the iron 



