M r. M acK enzie rep lied to th e discussion on his P a p e r in th e follow ing w ritte n com m unication :—
R e p ly in g to M r. Shaw , th e a u th o r sta te s t h a t i t w as n o t th e id ea to o b ta in from each ladle exactly th e sam e a m o u n ts of silicon, m anganese, etc. In fa c t, i t was f e lt t h a t th e in fo rm a tio n would be b e tte r if some v a ria tio n in these were allowed, an d , th e re fo re , sm all ta p s w ere ta k e n . I t is well k now n t h a t in u sin g h ig h p e rcen tag e alloys an d ta k in g o u t sm all am o u n ts, as was done in these e x p e rim e n ts, th e v a ria tio n s a re likely to be very serious. I n fa c t, in u sin g o rd in a ry m aterials, it is comm on p ra c tic e to use a receiving ladle so t h a t b e tte r m ix tu re s m ay be o b tain ed . I t should also be born e in m in d t h a t th e sm all cupola used was only 18 in . in d ia m e te r w ith a very low stack, so t h a t an excess coke h a d to ta k e th e place of th e stack , to some e x te n t, in h e a tin g . W e have tr ie d ra tio s of 6 to 1 of coke in all steel m elts in th is cupola, a n d w ere v ery successful in g e ttin g good te m p e ra tu re s , b u t w ith 17 p e r cent, ash coke th e iro n could n o t have been h a n d le d in th e ladle if such coke ra tio s w ere used. Also, considering th e f a c t t h a t th e su rface of th e cupola v aries w ith th e
first pow er of th e d ia m e te r, an d th e a re a v a rie s w ith th e sq u are of th e d ia m e te r, i t can be re a d ily seen t h a t m ore coke is u su ally necessary in a sm all cupola th a n in a m edium size. I n la rg e r cupolas o th e r fa c to rs o b ta in , a n d th is does n o t go to th e o th e r ex trem e. The sam e is th e a rg u m e n t fo r th e h ig h e r bed. W ith h ig h ash coke i t is n ecessary to p u sh a ir th r o u g h a v ery lo n g colum n of coke to g e t th e m ax im u m te m p e r a tu r e an d carbon dioxide. I f th e r i g h t bed h a d been used fo r th e B a r r e t t coke we w ould n o t h av e been able to m elt w ith th e h ig h ash beehive coke, a n d in o rd e r to keep th e co n d itio n s th e sam e, th e bed w as p u t a t a p o in t w here i t w ould w ork w ith th e se cokes, n o t w ith a n y id e a t h a t if we used B a r r e t t coke in a cupola c o n sisten tly we w ould ever d re a m of stic k in g to a 40-in. bed. O ur p e rso n a l o pinion is t h a t if we h a d to use D a y to n coke we w ould go to a 60-in. bed.
The te m p e ra tu re s o b ta in e d h av e been recen tly checked w ith th e U .S . B u re a u of S ta n d a r d s , an d th e re s u lts w ill be p u b lish ed by th e A m erican F o u n d ry m e n ’s A ssociation. T he w ork done by th e G rey Ir o n R e se a rc h C o m m ittee of th e A m erican F o u n d ry m e n ’s A ssociation on c o m p a ra tiv e te m p e ra tu re s betw een th e o p tic a l p y ro m e te r a n d th e therm o-couple shows t h a t ste a m te m p e ra tu re s give a p p ro x im a te ly th e o re tic a l co rre c tio n fo r all m ix tu re s , a n d th e a u th o r e n te r ta in s no d o u b t of th e ap p ro x im a te a ccu racy of th e se figures.
A bout th e heavy coke ra tio s , w hich w ere also m en tio n ed by M r. C am pion, i t is n o t f e l t t h a t th is h ig h a m o u n t of coke w hich w as selected as a m ere convenience in h a n d lin g th e m e ta l in sm all q u a n titie s because i t gave such excessive high te m p e ra tu r e s w ould ch an g e th e r a tio of th e d iffe re n t cokes w h atso ev er if th e a m o u n t w as c u t to , say 6 to 1. I n one case we w ere able to h a n d le all of th e m elt, b u t fit 6 to 1 we w ould n o t be able to h an d le th e h ig h ash coke a t all. I t is n o t believed t h a t th e re la tio n betw een th e d iffe re n t cokes w ould be c hanged a t all by th e ab so lu te a m o u n t of coke used.
R e p ly in g to D r. B eck er’s re m a rk s, th e a u th o r re g r e ts t h a t no figures w ere av ailab le fo r r e a c ti
v ity . I n fa c t, th e r e is v e ry li tt le u n a n im ity of o pinion as to th e c o rre c t te s ts. A re c e n t P a p e r by P ro f. P a r r , of th e U n iv e rs ity of Illin o is, seem s
to give a v ery u sefu l te s t w hich can be carried o u t on a la b o ra to ry scale. W e shall a w a it M r.
M o tt’s e x p e rim e n ts w ith considerable in te re st.
T h is te s t w ould seem to be a la r g e r scale modifica
tio n of P ro f . B a h r ’s, pu b lish ed in “ S ta h l un d E is e n ,” volum e 44, pag es 1 to 9 a n d 39 to 48. I t is h oped t h a t th e U n iv e rs ity of Sheffield w ill obtain some of th e m ore re a c tiv e cokes to supplem ent charcoal, w hich is th e u p p e r lim it of P ro f. B a h r’s ex p e rim e n ts. The a u th o r w ould be g lad to ship M r. M o tt a sam ple of th e B a r r e t t coke, an d prob
ably could o b ta in fo r him one of th e lig h te r p e tro leu m p itch es, if i t is n o t av ailab le in E n g lan d .
I n conclusion, th e a u th o r w ould th a n k M r. J . E . F le tc h e r fo r a b s tra c tin g th e P a p e r, a n d also for h is k in d ly re m a rk s. A g r e a t deal of th is w ork was done before th e id ea of a com plete series came in to b eing, a n d a g r e a t deal of in fo rm atio n which w ould h av e been o b tain ed h ad th e program m e b een c a re fu lly m ade, w as n o t o b tain ed in th e e a rlie r m elts. As i t w as n o t possible to re p e a t these, on acco u n t of th e e x h au stio n of th e coke supplies, some d a ta w hich w ere o b tain ed on the la s t of th e m elts w ere n o t p u t in to th e tab le.