982 IRON 



of sulphur in cast iron diminishes in proportion as tho amount of limo in the slag 

 increases. A still better flux is oxide of manganese, and it is found that when tho 

 manganiferous spathose ore constitutes part of the burden of the furnnco, sulphur 

 almost entirely disappears from the crude iron. M. Janoyer believes that ho has 

 proved experimentally, that the whitening of cast iron smelted from sulphurous ores, 

 is due, in part at least, to the subtraction of a portion of its carbon, and its volati- 

 lisation in the form of sulphurot of carbon, by which the temperature of tho furnace 

 is lowered; but his experiments on this point require confirmation. The presence of 

 a very small quantity of sulphur acts very injuriously upon bar iron, so small a pro- 

 portion as Yojjoo rendering tho metal 'hot-short,' that is, incapable of being worked at 

 a red-heat under the hammer. If tho quantity of sulphur in the crude iron exceeds 

 0'4 per cent., it is scarcely possible to manufacture it into good wrought iron. 



Silicon. Like carbon this element enters into combination with iron in all propor- 

 tions up to as high as 8 per cent. The largest quantity found by Karsten in pig- 

 iron was 3*46 per cent., but in the above table a specimen (ft) is quoted from Coal- 

 brookedale containing 4'88 per cent. : and Dr. Noad found it in a sample of Nova 

 Scotia iron, as much as 5'8 per cent. Generally speaking, grey cast iron contains 

 more silicon than white, and the greater the quantity of graphite in the crude iron the 

 larger the amount of silicon, because the higher the temperature of the furnace ; but 

 this again will depend materially on the quality of the coal, from the ash of which tho 

 silicon is probably principally derived. A clean strong coal yielding a small per- 

 centage of ash furnishes a cast iron with less silicon than an inferior coal, the mineral 

 burden being the same. Pig-iron smelted with hot blast contains more silicon than 

 when the blast is cold, because of the higher temperature which prevails in the fusion- 

 zone of the furnace. Some analyses illustrating this fact have been already given. 

 According to the experiments of MM. Janoyer and Gauthier the amount of silicon 

 in hot-blast cast iron may be greatly influenced by varying the proportion of lime- 

 stone in the furnace. Pig-iron obtained with a charge yielding a cinder in which the 

 lime and alumina were to the silica as 7 is to 10, had little strength, breaking readily, 

 and analysis showed that it contained 3 per cent, of silicon. By increasing the amount 

 of lime in the charge, so as to obtain a cinder in which the bases were to the silica as 

 8 is to 10, and at the same time employing a blast of the highest attainable temperature, 

 the iron produced had a much greater strength. When the proportion of bases to 

 silica in the cinder was as 20 is to 19, the iron contained only an inappreciable amount 

 of silicon, and the strength was increased in the proportion of 65 to 45. When the 

 maximum quantity of lime was used, the consumption of fuel was on the average in- 

 creased to the extent of 6 per cent. 



The experiments of MM. Janoyer and Gauthier induced the furnace manager of 

 the Blaina Iron Works to increase the yields of lime on one of his furnaces to as great 

 an extent as in his judgment it would bear, and when the furnace was under the full 

 influence of the excess of flux to forward him samples of the grey pig for analysis. 

 The following results show that, contrary to the statement of MM. Janoyer and 

 Gauthier, no advantage, as regards a diminution in the amount of silicon, was hereby 

 obtained, the proportion of that element being not perceptibly altered, though there 

 is a slight diminution observable in the percentage of sulphur. 



Grey pig, with usual Grey pig, with extra 



burden of lime. burden of lime. 



Sulphur .... 0-067 .... 0-045 

 Silicon . . . . 2-900 .... 2'930 



As the presence of silicon in pig-iron affects in a remarkable degree tho yield as 

 well as the strength of puddled bars, it is of importance that this element should bo 

 removed as effectually as possible by a refining process before the crude iron is sub- 

 mitted to the puddling process. Pigs with 3 per cent, of silicon gave about 6 per 

 cent, of silica, and this requires somewhere about 12 per cent, of iron to form a cinder 

 sxifficiently fluid to allow the puddled iron to become aggregated into balls; this can 

 of course be obtained only by burning that amount of iron in the puddling furnace 

 after the expulsion of the carbon, and while the mass is in a powdery state. This 

 powdery mass is composed of small granules of iron mixed up with a gluey infusible 

 cinder. The puddler turns over this mass repeatedly to expose the iron to the oxidising 

 influence of the furnace ; tho silica now taking up sufficient oxide of iron to give it 

 fluidity begins to separate from the iron, and forms a pool at the bottom. After some 

 time tho puddler, finding tho mass of cinder accumulating pretty fast, makes the first 

 attempt to ' ball up.' In order to save as much iron as possible, he keeps the damper 

 down and works the powdery mass at as low a red heat as possible. Tho balls, even 

 when made, will not bear much heat under tho hammer without falling to pieces, 



