[ 289 ] 



LT. 'Experiments to ascertain uhether there exists any 

 yiffiniiij letwixt Carhon and Clay, Lime and Siiex, se- 

 parately or as Compounds united with the Oxide of Iro?i 

 forming Iron Ores and Iron Stories. By David Mushet, 

 Esq. of the Colder Iron-lVoiks. 



[Continued fiom p. 201.] 



i-N order to ascertain whether there existed any affinity 

 betwixt carbon and calcareous earth in high temperatures, 

 amounting to a fusion of the hitter, the following experi- 

 ments were made with the tour following substances, viz. 

 calcareous spar, chalk, Kilkenny marble, and pure calca- 

 reous earth. 



Before I begin this detail I think it proper to observe, 

 that when no particular nature of crucible is mentioned, 

 one of Sturbridge clay is always implied. The carbon used 

 was formed from the burning of lamp-black, which was 

 found to contain less ash than any other charcoal I had 

 tried, and therefore less likely to injure the results by any 

 premature degree of fusibility arising from such a mixture 

 of ash. Its purity was further inferred from a superior affi- 

 nity to iron, not only more instantaneous, but more exten- 

 sive in its effects than either charcoal of wood or that made 

 from animal substances. Oak forms frequently a very pure 

 charcoal, containing not more than 1-I50th part of its 

 weight in ash. Lamp-black contains not more than 

 1 -280th part ; and its tendency to revive a given quantity 

 of oxide of iron was found, upon the average of five experi- 

 ments, to be to the former as 63 to 58. 



The tops of the crucibles were accurately ground, and 

 the covers made to fit nearly air-tight, '^ilie n)atter to be 

 operated upon was introduced into the crucible while the 

 latter was at a red or bright red heat, and the cover, in a si- 

 milar state, simply put on, and both introduced into the 

 furnace. This mode of operating is infinitely more accu- 

 rate than luting, and using a green crucible: mdeed, these 

 experiments could never have been made within a loodth 

 part of the truth in tliat way. A quantity of the water, which 

 IS necessary to give softness and plasticity to clay, remains 

 after drying, and ultimately evaporates as the heat to which 

 the clay is exposed increases. If charcoal is presented to it 

 in this state it disappears in great quantities, and renders 

 any experiment as to quantity extremely doubtful. 



Vol. XVIII.N0772'. T Expe- 



May 1S04, 



