148 On the different Proportions of Carbon, &c. 



crucibles fmaller or larger, or with a greater or lefs weight of 

 mixture, would not obtain the fame remits. 



The formation of caft fteel in the large wav, founded upon 

 the refultsof the foregoing experiments, affords an incontefta- 

 ble proof of this. In fufions of 18, 22, and 25 lbs. of iron 

 each, we are obliged to increafe the dofe of carbon considera- 

 bly beyond that requisite in fmall experiments. To form 

 iieel equal to that obtained in experiment XIII. wherein -th 

 of charcoal was ufed, ^th part is requisite to be introduced. 

 For fteel Similar to that in experiment XIV. ~ T th and ,,\ th 

 part are ufed. For fofter fteel -^tb, whereas in the fmall 

 experiment -r-i-^th P art was fufficient. If in the manufac- 

 turing a fmall extra quantity of carbon is requifite, this li 

 faved by the comparatively fmall lofs fuftained in the tranf- 

 mutation of the iron into fteel. 



Many initances have occurred in the firft fufion from a 

 caft fteel pot in the large way, where 25 lbs. of iron, and its 

 requifite proportion of carbon, not exceeding yoth, have af- 

 forded an ingot of caft fteel weighing 24 lbs. 12, 13, 14, and 

 15 ounces, being a lofs equal to no more than -rj^tki v£tf&t 

 T-To l h, T^, tn P art tne weight of the iron, whereas in expe- 

 riments No. XIII. and XIV. the lofs of metal amounted to 



--— th, and — g-th part the weight of the iron. 

 3 1 1 * 2 2 Vo 



I Shall conclude this paper with a few remarks upon the 

 irate in which carbon exists in fteel and in crude iron. 



When malleable iron is fufed with T y-oth or -p—th part of 

 its weight of carbon, the refulting product is considerably 

 itceliflea. The fracture is lighter in the colour than it for- 

 merly was in the State of iron. When fufed with an 80th 

 to Tr '- C th, fteel of an ordinary quality is produced, the frac- 

 ture of the metal ftill becoming whiter. When the dofe of 

 carbon is increafed beyond this, the fteel becomes fo hard 

 and denfe as to be unfit for hammering. The fracture now 

 will be found approaching to the colour of Silver, and lofing 

 its granulated appearance, afTuming, however, a cryftallized 

 form. In this ftate the metal will be found to refift the 

 hammer ano) file, and to be unfit for any purpofe. Increafe, 

 however, the quantity of carbon to T \th or -/3 th, the refult- 

 ing product is no longer deftitute of grain, nor pofTelTed of 

 the lame degree of hardnefs. The fracture will be found 

 gray, and the furface eafily reduced by the pile. A further 

 increafe of the carbon is accompanied by an increafe of thefe 

 properties. At i-8th or I -6th, the filings of the metal, 

 when thrown into water, leave a carbonaceous pellicle cot 

 vering the whole furface, and of a confiderable thicknefs. 



Thus 



