ON BLAST F U R N A C E SLAGS AND THE F U S I B I L I T Y O F SILICATES.
BY X L X ~ S , T J. E ROW. Blast furnace slags are, with pig iron, the ultimate products of t,he reduction of the charges, their composition depending on t h e proportion of the different earthy elements contained in t h e ashes of coal, in t h e limestone and t h e ores, a t least, of such elements as can form fusible compounds. As such, they are the real criterion by which a skillful manager will judge of t h e economical rniining of his furnace. I n general, other things being equal, t h e composition cf the slags directly affects their fusibility and bears a close rclation t o t h e grade of iron obt,ained. Certain conditions corresponding to a comparatively low temperature in t h e furnace require also a very fusible slag a n d a readily fusible iron. Within certain limits, t o be mentioned later, such a temperature may be sufficient to melt slags of a somewhat different composition, and t h a t slag which requires t h e fusion of the least quantity of foreign matters, will be, obviously, t h e most economical a n d advantageous. Works on metallurgy contain many analyses of slags, often of little value, hecause neither t h e composition of the materials charged, their relative proportion, nor t h e character of the resulting pig metal are mentioned. There is no way of deducing-from t h e composition of the slag-its economy under given conditions. A blast furnace is as much a chemical apparatus as any t h a t is used. Chemicallaws govern the reactions which take place in i t and metallurgists often find in practice t h a t t h e composition of slags calculated from known charges, agree almost as closely as duplicate analyses. It is very desirable t h a t all analyses of slags published should be accompanied by the data pertaining to each case. The writer has collected t h e analyses of a great number of slags from European and American furnaces, many made by himself ; with most of them he has been able to ascertain t h e accompanying conditions, a n d in all t h e general conditions and the character a t least
of the pig metal r u n with them are kiiown. I t has seemed to him t h a t some information on a subject so importarit for iron workers would be of interest. T h e works of Uerthier, Caron, Ebelnien, Percy and others, on the fusibility of silicates, liave been precious contributions to this question, hiit they are not generally well kiiown to those who would find them riiost useful, owing perhaps to the preconceived idea t h a t they are too technical. I t is intended t o quote from them practical data exclusirely, showiiig, by a few examples, that t h e conclusions which these metallurgists have reached are fully corrobor:lted by blast furnace pract,icc. Tlie present paper will be limited to t h e subject of fusibility of silicates so far as connected with their coniposition, with economy of working a n d character of pig mct:ii. Many circumstances may modify results sometimes foreseen, and to say t h a t 3 slag of a certain compositidn and fusibility will invariably correspond to il stated grade of iron is inipossible. Still, it will be fonnd that divergences, wlicn well marked and decided, can generally be traced to certaiii special or abnormal conditions. rl'lic determination of the empirical or rational formula of a silicate preseiits no difficulty to the technical chemist, b u t it i i i volves it kind of knowledge which many iron masters. otherwise t h o r o u g l i l ~competent, do iiot always have a t conimuncl. Slags are coml'lex silicates, principally of alumiiiit, lime itrltl magnesia, b u t contaiii i ~ l s o ,arid normally, notablc percentages of ferrous and riiaiiganous oxide, potash, sodti and b:tryta, anioui~tingt o iis much iis 7 aiitl S per cent. T h e presselice of these elements ill quantities which caiiiiot be neglected i n ascertaining thc tFpe of a silicate, still further coiiiplicates the calculations. The composition of a sl:ig, tlic perclentage of its constituents, rarely :tffords, a t first sight, a clear conception of its chemical character. comparison with others, if it a n be easily macle, m a y be of great advantage. Given the percentage of silica and of the different bases, by B simple calculation and a table given below, without the use of any chemical symbol or-fornzuln, the character of a slag, its approximation to a certain chemical type, can be ascertained a t once. The method is given in full.
BLAST FURNACE SLAGS, ETC.
191
Blast furnace slag is a combination of silica with various bases, principally alumina, magnesia and lime. T h e ores of iron contain, as gangue, silica associated with certain earthy or alkaline bases and almost invariably a n excess of free silica as quartz. Should snch an ore be smelted without any addition of fluxes, the free silica, not finding a base, would combine with a part of the oxide of iron which i t would remove as slag. This is what takes place in the Catalan forge, where the slag is obtained a t the sacrifice of a certain quantity of iron. Fluxes are then added in the form of limestone or dolomitic limestone, of which as little should be used as is consistent with the proper fusibility of the silicate formed from the silica of t h e ores and t h e ash of the coal with the bases found in the latter and in the limestone. Owing to the complexity of the silicates as componnds, t h e theory of them is still obscure and, in t h e following, we do not pretend to deal with theoretical considerations, but only with slags as they appear in books on metallurgy and as they arc practically known to ironmasters. I n the composition of slags as given in these works, u p to a comparatively recent date, the symbol SiO, isused for silica, which was for a long time regarded a8 a ‘‘ trioxide.” T h e equivalent of silicon was then taken a t 22.00 bysome, a t 21.25 by others ; i t is now assumed to be 14.00 ; at. wt. Si = 28.00. T h e equivalent of silica, SiO,, was consequently.takcn as 46.00 or 45.25 as the case might be, t h a t of SiO, is now 30, mol. wt. GO. The oxygen of silica calculated from the oldformulaSi0, was then : =0.530or = 0.533. I n the .same manner the equivalents 0 . 5 2 2 . I t is now of lime, magnesia and alumina, as late as 18G5, were sliglitly different from what they are assumed to be now, that of lime being taken at ‘78.25, which is now 28.00; at. wt. 56. All these differences affect only the hundredths of the composition as given in these books. SiO, will be used here for silica, unless otherwise mentioned. All the f o r m u l s of slags are expressed in equivalents, (and not in the atomic weights) in all books u p to 1886 and even later, and this practice will be followed here. Whatever may be said logically of the consideration of silicates as derivatives of certain hypothetical radicals, t h e use of the equiv-
is
:$t-
d e n t s has, in this case, the advitiitage of representing clrarly to the eye a certain relation of silica to bises, and of the oxygen of t h e acid t o the oxygen of the ~ H S C S ,coriwpontling, in general, to :t i'tnrtiiiii gradc of iron. T l l c . tiiiPcrciit c;irths n o t only s:ttur:ite d i f f c > n , i i t yriaiitities of silica accoidiiig tc tliei? cyiiivalents. hit, for thv saint! base, tlic proportio~isof t h c basic cltaineiit t o t,liRt of thc ttcid n i i i y vary. 'Yhc rcsiilt of :ill olisi,rv:it,iotis s l i ( ~ wtlirit c o t i i p o u ~ i d:IS i v c ~ l l a; simple 1)otlie.jcoriiliitir togetlicti iti :I. certabiii ntiiiilitii. of l)ro1)oi't io Ii s (1i st i 1 i c tl y il c t c' r ni i i i c ~ l \ ~v h i c l i ;Lr(! gen ern1 1 J- t o i r i sinil)lc ratio, :it least w l i e t i ivc d i d with iirttiirii! itiitior:tIs. l:or iiistitticc, 1. ?, 3 of linic. niagiic~aia or, i i i goiic-.r;i:.( i f iac:li utlic.1. oxides of synibol IiO, w i l l c o i r i l i i i i c l wit11 tlic i i t r i i o ilii:tntit\- 1 :!f sili(8iL 01' coiivcrsc~ly: so also will : ~ l i i r n i n ; i o r isomoi.plioii~oxiilos,, lt*()3. tlioiigli i t i t1ifft:rcaii t 1)roportioiis. I%l:L,t I'iirtia(xas ..liigs coi~sideicd:LS sili(:txtes of l)rotosiilc niny \)c : ;icid, iicutral? s c x i l i i i basic-, bibasic or, occ:~sio~~:illy. trilxisic. Sesqiii:ici(lslags c ~ o r i ~ c s p 0 1 i d to "types i n wliicli tliew is respec*tivcly: 1 of I)~tscto '! of ;ii,ici (it(:id): I 01 b:is~to 1 of acid (1lcutr:il) : 1.;- of h i a t . to 1 of itcid: oi', 3 of b t m to 2 of acid (sesquibasic) ; ;! of I J ~to ~S 1 ofOacid [ l i b i t s i c ) ; :J of lsasc to I of acid (tribasic): 1 of base to 1: of acid or '! of L:isc to :I of wid (sesquiacidj. 'l'hcir forniulw art: liO,? Si0 IiO, SiO, :)IEO>:?SiO, .?IiO, S i 0 tjI10, Si0 ?RO, ;ISi 0 , -\c i (1, I 1e ii t I-aI, scsq 11i basic. 1) i ti:t s i v. t r i b:i si c n11 (1 sesq ii i ttc i (1 and tlie ratio of oxygen of the silica to that of tlie base i s resprcth e l y for each : ( j .,- or :::1 1:l .) * *.1 4:3 1 :1 . Many other silicates fall between these types and are met with in dags. To form a neutral silicate, that is one in which the oxygen of the acid is double t h a t of the base, the bases of the formula R,O,, require 3 atoms of aciti. Herice, the neutral silicates in R,O, take the form R,O,, 3Si0, ; the acid silicates, 1 base to 2 of acid, will be represented then by R,O,, GSiO,, the sesquibnsic, 13 base to 1 acid, by 1-4Rz0,, 3SiO,, or, 3R,O,, GSiO,, or, R,O,, 2SiO,, and, indeed, oxygen of acid 4, oxygen base 0::4:3. In t h e same manner the bibasic silicate in R,O, has for its formula : 2R,O,, 3Si0, ; the tribasic, R,O,, SiO, ; t h e sesquiacid : 2R,O,, y S i 0 , . If we insist on these points i t is because these "
,
.).'I 1
.)
.i)
193
BLAST PURh-ACE SLAGS, E'PC.
formule are constantly met with in metallurgical hooks, in which slags are called by the preceding names. As we shall frequently find formiils in which the silicates are expressed by SiO,, we must be able readily to transform one formula expressed in SiO, into onc in which SiO, is used, or conversely. For this, the following method will be found convenient : ~ ~ C L E - Tconvert O the formula in SiO, into the oldw formula in which silica is rttgardcd as ft trioxide : Nnltiply the entiveJir~iii?~ln by 3, correct the silica term by the equation SiO, = 3 SiO, and reduce the whole to its lowest terms. For instance, if to transform tlie formilla, RO, SiO,+R,O,, 3Si0, which represents a neutral silicate of KO and R,O,, we multiply by 3, me have : 3110, 3Si0,+3R,O3, OSiO,; but since : lSi0 = iSi0, ; 3SiO,= 2di0, ='?SiO, =GSiO, OSIO, = GSiO,, and the old formula would be, for the s t m e compound : 3R0, ?SiO,+BR,O,, 6Si0, or, reduced, 3 K 0 , 2Si03+R,0,, 2Si0,. Conversely : to change formula containing SiO, into one containing SiO,, divide a17 terms by 3 and correct the silica term by SiO, = j$ SiO,. We have p u t i n Table I. the new and old formule for silicates of the same chemical character, giving also for each the oxygen ratio of bases in RO to oxygen of bases in R,O, and the ratio of the total oxygen of the bases to t h a t of t h e acid.
- --
,
TABLE I. NEW FORJIULA : SIO1.
Corresponding to :
Equiv ....S i O a = 1 4 + 1 6 = 30 At.wts. ... = % 3 + 3 2 = 6 0 Oxygen silica = @ = 14 = 1= 0.593 of 80
90
15
sioa
(A.)--ddd Silicate. 2 Equiv:'acid to 1 bt?e RO 6 to1 R103 Oxygen ratio.. . . . R O . ..HaO,. .Si01 1 : 1 : 16 Formula.. . . . . .RO,2SiOp RaOt, 6SiUa 0 of acid : Oof bases :: 16 : 4 = 4 : I The disilicate of modernnomenclature derived from BaSilOl = HaO, 2SiOa ; 0 ratio, 4 : 1 .
. ..
-+
OLD FORXCLA : SIO~.
Equiv ..........._.. Si03=21.26+21=41.25 24 Oxygen.. . . . . ..Si03 = 21.15= 0.5304 of SiO,
...
(A).--No correqmding name &ven by P c r y . Oxygen ratio.. . . . . RO - RIO, Sip3
. . .. ..
3 : 3 24 1 : 1 . 8 Formula., . . . . . . , ..3RO, 4Si03 RIO;.&io3 U of acid : 0 of bases : 24: 6 = 4: 1 In accordance with other name@,based npon SiO,. this would be a qwd&Uieate.
or
+
194
BLAST PURZU'A('E SLAGS,
ETC.
TABLE I.--Contiizzietl.
to 1 b y e KO to 2 HO 9 .. to:! H.0, 0 . ratio.. . . K O . . . I f a 0 3 . .SiO, 2 : (i : 2 1 o r l : : i : l ' J 1% Eq.d i:
or R
..
.
, . I W . . . R , O , . SiO, 1 : 3 ' 12 Formnla. . . . . .KO, S i o s + K,O,, 3Si0, 0 of w i d : 0 nf bases : : 12 : 4 7 3 : 1
0. ratio
+
Formiila. ... .2RO. 3Si0, P R , 0 3 . 9Si0, 0 of acid : Oof basee : : 1 2 : 4 = a : 1 Trisilicate derived from H , q i 3 0 8 = OH+. 8Si0, 0 ratio = 8 : I
_-
I
.
.
C.)--~Veutrnl Silicatr.
I Eqiiiv. x i d t o 1 b y e KO 9 '( to 1 Iaeic Silicale. 1 w i d t i l 1% b y e R O or 2 " toX RO .
_ _- - - - _
..
ti w i d to 8 bijfe R,O, 0 . r a t i o ...3 : X : 8 or !! to 1 K,03
.
Formula . . . . . . . . : 3 l ~4S10, . ?- R , 0 3 . 2si0, 0 of acid : 0 of babe? : H : ti = 4 : 8 A dibilicnte o f modern type derived from I1,sipU, = %II,U) 2si0,. 0 ratio 4 : !i.. 1 arid to 2 IIHWRO :3 t o 2 " IL& 'I
0. ratio ...2 : 6 : 8 = 1 : :3 : 4 Formuln..2HO, NO, 2A20,. 3Si O e 0 of acid : 0 of baser :: 4 : 4 = 1 : 1 T h e mono6llicare ba4c of modern noiilciiclature, derived fr&n orrhosiiicic arid 11,510, = 2(8,O)YiO, : 0 ratio 1 : 1
.+
Tribn,w StNcu/(
((+.)-
1 w j d to 3 bnee RO
R
or
i
0.ratio ...4 : 9 :
13
4
tn?
11
ir;
./
+
i
17.n.
iiitj
Formula..YRO, SiO. R,O, NOI O o f acid : O b f bairn-:: 4 6 = 2 : 3 T h e monosiiicate parasilicate of modern nomenclature, dehved from H6SiOb = 31H,O) SiOzl 0 ratio 2:3. - ....
.
(E.)-No special name by Percy. 0 . ratio. . . . . . . . . . . .RO R 0 S i 0 0 : !L :, 24
--
0,"
:3 : :3 : R Formula.. , , .YRO, 4Si0, +4R103. 4Si0, 0 of acid : 0 of basee : : 2 1 : 18 = 8 : 0 = 4 : 3
0. ratio . . . . . . . . . . . . ...4 : 4 : 6 or 1 : 1 : 2 Formula , , . , . . , , , . , .3RO, SiO, R a 0 3 $ios 0 of acid : O o f bises : : % : 2
+
= I : 1.
tG.)- No upecial name by Percy. 0. ratio . . . . . . . . . . . . . . . ?. : Y : 12or d ' 2 . d
Formula ... 9RO ZSiO, i-3RaO,. 2SiO 0 of acid : d of bases : : 12 : 18 =%: 6 =a: 3
-
._____-
BLAST FURNACE SLAGS, ETC.
195
It will be seen t h a t t h e ratio of oxygen of acid to t h a t of bases is the same in both formule, as i t should be, since : 3Si0, = 2Si0, as far as oxygen is concernecl ; and also as to t o t d equivalent; 3Si0, = 90, using present equivalents, or 2 x 45 = 90, using the old equivalent assumed for silicon. This ratio of oxygen of acid to oxygen of base is t h e most characteristic .fentnre qf a type of silicates, whatever may be said of their exact molecular composition. When i t is found to be the same in two silicates containing different bases in different’proportions i t oorresponds to the same calciilated empirical formula for each, to the same saturation of bases and acid and the same fusibility, the conditions of temperature determining the production of such slags in a blast furnace arc similar, in other words, they are likely to accompany the same grade of iron. I n a question of such importance as this, involving references to works ih which notations and nomenclature i t r e different from those now used, it is necessary to establish a clear basis of underst and ing. Using t h e symbol SiO, for silica, Percy and others have called a neiitral silicate or trisilicate a silicate in which the 0 of base : 0 of acid : : 1 :3. Hence, RO, SiO, represented for him a trisilicate. Now such silicate, with SiO,, corresponds to a sesquiacid silicate 2R0, 3Si0,; 0 of silica, 6 : 0 of RO, 2 : : 3 : 1 : the neutral silicate of our days being one in which 0 of acid=2 X O of bases or RO SiO,, silica being a dioxide, not a trioxide. I n R,O, this neutral silicate of Percy has the formula R,O,, 3Si0, (0 of silica, 9 = 3 ~ 3 t i m e s 0 of base). Now: 213,03, 9Si0, (0 acid 18=0 base, 6 x 3 ) . I n the same manner he called a sespibasic or bisilicate a silicate in which 0 of acid=2 x 0 of bases, 3K0,2Si03; R203, 2Si0,; now : RO, SiO,+R,O,, 3Si0, (neutral). He called a bibasic or sesyuisilicate a silicate in which 0 acid : 0 bases: : 3 : 2 ; 2R0, SiO,, 2K,O,, 3Si0,; 0 ratio; 3 : 2 ; 9:6=3:2. Now: 4RO,3SiO,+4R,O3, 9Si0,: 0 ratio; G:4=3 : 2 ; 18:12=3:2, a n d does not correspond to any of the types under SiO, mentioned in t h e table I. He called 3 tribasic or monodicate a silicate in which 0 of acid= 0 of base, now called bibasic : 3R0, SiO, + R,O,, SiO, ; now : 2R0, SiO, +2R,O ,, 3SiO
,.
111 all t h a t follows when tlie terms (icid, 1 ~ e i i t ~ n etc., 1, silicate a r e used, reference is made to silica expressed by the symbol Sit)?, and not by SiO,. uiiless otherwise mentioned. I n t h e modern conception of t h e compositioii of tlie silicates, noi~mal hydrated silicic acid 11as the formula 11, SiO,(=BII,O, SiO,), a tetrabasic acid containing 4 atonis of hydrogen which c;tn be replaced by metals. I t lias iiot becii isol:itetl, but i t is prob;tl~le t h a t it exists i i i t h e 1~seti(lo-so~utii,iis coming from the dialysis of liquids containing alkaline silic;ttos. T h e nietiisilicic h y ~ l r u t cis formed when solutioiis of didyzctl silicic liydrate are erapoi*:ited. I t is probable t h a t metwilicic mitl C : L I I Lu coiideiised i n t h e sitme way as meti%phosphoric m i d to fd1.111 cornpies molvculci: ( J f polyaiiicic acids. 'Tli~~rcare kiiowil : oi~tliosilicates, 2 R i I . SiO,. ( : O I ' ~ H S poiitling t o t h e iiorrn:tl hydrates (bibasic silicates of table I ) : monobasic silicates, 110, SiO, (neutral), which seems t o IJOticrived from inetasilicic acid. 'I!ht~ real moleculiir constitutioii of tlie polysilicates is ignored. 111 most of the lorinnlit> oiic: is satisfied to. c.xpress tlie ratio of oxygen of si1ic;t to oxygen o f hises. 111 the orthosilicates (bibtisic) i t is 1:1 in t h e metnsi1ic:ites ( n e t i tral) 2 : 1; i n t h e trisilicatcs (sesqtiiacid) :3: 1. e. [I., or tliosc, *?lZOt 3Si0,. I n h s i c silicates (serpentine type) 4::3 jsesyuibasic). T h e r e are other basic silicates in wliicli it is 3: 2 (dysthene).* Although 110 solid hydrate of silicic acid possessing i t constant composition is known, we are acquainted with a large ~ i u m b e rof siIic:ttes forming many natural niiiieral species. * ' 'I'he hypothetic:il acids or hgdrogcn salts from which they are supposed t o Le clerivcd w e here given. " " Molecular weights liave been ascertaiiietl only for tlir volatile organic silicates or silicic ethers, the molecular weight of tlie other compounds is therefore d o u b t f ~ i :l tlie osygeii ratio being t h e best criterioii t o classify them ; their formill:? are represented by the simplost form possible." (Roscoe ti Scliorlemmer's Chemistry.) Also, from another authority. " B u t scarcely any of t h e silinates are represented by f o r m u l ~which express their derivation from t h e acid. TT,SiO,; or other hypothetical radicals. They are geiierally represented as combinations of metallic oxides with
* FrBmy.
BLAST F U R N A C E SLAGS, ETC.
197
SiO," (Bloxam's chemistry). It is this mode of representation t h a t we have adopted, using the equivalents and the formula SiO,, for silica. I n this manner the slag of composition, GCa,SiO,, AI, (Si04)3, using atomic weights and derivation from hypothetical radicals, would be represented by t h e formula, 12Ca0 ; 2A1,0,, 9Si0,=6(2Ca0,SiO2) +2A1,0,, 3Si0, (0 of acid = 0 of bases), which, referring to Table I, represents what we may call a bibasic silicate with RO and R,O,, derived from the orthosilicic acid ; H,SiO,= 2H,O,, SiO,. A monosilicate ; orthosilicate according to modern nomenclature, (Table 11). 0 of acid = 0 of bases. The tribasic or /nonosilicate of Percy, 3R0, SiO,+ R,O,, SiO, (0of acid = O of bases) (Table I). TABLE 11. JIOSOSILICATES.
1" Xetnsilicic w i d : H,SiO, = H , O,SiO,, forming monosilicates (monobasic) 0 ratio 2: 1 corresponding to RO,SiO, (neutral), MgO, SiO,. Augite (Ca, Me;) SiO, = Ex. Enstatite Mg, SiO, A12 1 0, 3Sio2 Be, ~ o , , ~ ~ O.'?SiO,-Beryl. i::(Si0,)3 = Be, -41% 0 ratio 2:1. 2" Ortl~osilicicacid H,SiO, = ? (H,O) SiO, forming bibasic monosilicates. 0 ratio 1:1 Corresponding t o 2RO,SiO, (bibasic); 2H,03,3Si0,-Ex : Olivine, Mg,,SiO, = 2MgO,Si0, ; Phenakite, Be,SiO, = 2Be0, SiO,. 3" Parnsilicic acid = H,SiO,= 3 H z 0 , S i 0 , ; Oxygen ratio 2 : 3 forming monosilicates corresponding to : 3RO,SiO, (tribasic, 0 r'itio 2:3). Ex: Chondroditc Mg,,SiO, = 3MgO,SiO, ; Andalusite, AI,SiO, = Al,O,,SiO, (tribasic silicate) = A1,0,#Si033A~,,0, 2Si0, 0 ratio = G: 9 or 2: 3 as before. DISILICATES.
H,Si,O,
= Hz0,2SiO,
0 ratio : 4 : 1 corresponding to RO, Ex : Petalite
2 SiO, (acid silicate) 0 ratio 4 : 1, = 3R0,4Si03 I
acid silicate,
+
4A1~O34Si0, v
an acid silicate in SiO,; 0 ratio 12 : 3 = 4 : 1.
~o,
198
HLAST F U R N A C E SLAGS, ET('.
H 6 S i z0 , = 3H, 0,8Si0,;0 ratio 4 : corrcsponding to 3 K 0 , 2Si0, (sesquibasic) E x . : Serpentine, Jfg3,Si2(.), = :IMgO. i!SiO, 9Mg0,4Si03 (sesclaiibasic) O mtio 1:' : 9 = 4 : 3. H , , , S i 20 , = f g ~12.39 1 above, and to tlie remarksof Hertliiei-, ought t o be a CaO 15.05 I very fnsible slag. 1:irst : I t is a i i e u f r n l ' slag, not ~ 1 2 0 10.97 , ) ver:basic, coiiseqnentiy, silica is above -10 pein cent., _I nearing tlieliniit of(j0 perceiit. ~{asesin KO=SO.'; '"*'si =nearly 3 x I O . ! ) ~tlie , \ m e s in H,o,. Its formuia is UO, S10, + H,O,:I S i 0 2 , T h e ii.011 1'1111 with it ought to be wliite 01' a t least of ii very light grade of gray. 'These deductions made, I[ priori, from its composition, froni :t btuily of the fusibility of silicates, find tlieir verification in tlic actu;tl rcsults obtained i n a blast fnrriace in England. This hypothetical slag is identical, as far CLS type is c o n c e r t i d , w i t h one actually r n n in conditions indicating plainly a low temperatnre in tlie furnace, i. o . , a very fusible silicate. If, by proportioniiig properly the chargtx so as t o obtain it, it were found to be more economical in use than those of the Englisli slag, the two types being alike, ,111 t h e probabilities would be-the conditions of raniiiiig of t h e f n r n w e being t h e same-that the same grade of iron would be obtained, but, in one case, much more economically than in the other. Percy gives tlie following analysis of the slag of a charcoal furnace. Working as 'iir?Lite pig w i t h a little of light niot!Zed-consequently of a slag r u n at a low temperature.
SiO,
BLAST F U R N A C E SLAGS, ETC.
209
If t h e formula of this slag were calculated it would be found t o represent exactly, to thesecond CaO - - . 25.67 decimal, a typical ?ieufrnl slag. A l s o , - . 13.04 Itsformula is: 2.09 R,O,, 5.97 SiO, + 8.60 120, F e O - - - - 2 - 4 4 s.50 si02 or (R,o,, 2.96 SiO,) 2.02 + 8.00 M ~ o - - -2-20 (1.01 Ita, sio,) i. e., nearly as possible lt,03, 3 SiO, + RO SiO, : 0 of acid : 0 of bases : : '2 : 1; type neutral, and of the two slags, t h e typical one would liave been obtained at the least expense, since, while containing about the same amount of alumina, 10.97 per cent against 13.04, and silica 54 against 58.04, it contains only 18 per cent of lime, as against nearly 26 per cent. in the other, or 50 per cent. less. A doZomitic limestone would have readily furnished the 13.04 per cent, MgO without using the excess of pure calcite with only 0.57 MgO which were necessary to obtain the 25.67, CaO required to make u p for the deficiency of bases. T h e formula gives of course, the means of comparing these two slags but for the determination of the oxygen of the compound a knowledge of the symbols and equivalents is absolutely necessary, a glance a t the two analyses not furnishing sufficient indication as to the similitude in chemical type of the two compounds. We see in this case t h a t silica is about the same : 54 and 5876, t h a t the total proportion of bases is 42.00 in one case, against 43.92%in the English slag ; but, in the typical slsg, we find 18% of lime and nearly 13% of magnesia, while the English slag contains more lime, nearly 50% more, and n o magnesia, and the apparant coinsidence of quantity of silica and total quantity of hasic elements cannot be taken as a criterion owing to the different saturation of the bases for SiO,. I t can hardly be said t h a t the two compounds are of somewlint the same nature, certainly they do not seem to be identical in type as they really are, nor could i t be said t h a t one had been obtained with a much greater economy than the other. No deductions can be drawn from their composition except through a study of their formule. Suppose t h a t in t h e hypothetical slag a certain quantity of magnesia (8$) were replaced by a p o p o ~ t i o n a t eq u a n t i t y of lime according to t h e equivalents of these two bases, which express also, in this case,
Si0
~6 _=_ _ 54.00 o,57
1 J
their sntzimfioi~.fbrSiO, ; also that ii q t ~ i i i t i t gof 10%of alumina. were replaced by the equivaleiit proportion of linie according to wtnration of this latter base for SiOz, :IS csplaiiied above : that, is, tit tlie rate of 1.b31 lipie for 1 o f :tliiniiiia and 1.40 limo for 1 of niagiiesiir. I t is clear that tlie silicate has preserved its c'li;tracter, its type, the sntzirrrfio,( qf ,3i0, /I!/ ( h e bises m / ~ u i / ~ O thi,/ y.NOUC, h o t its composition is coiisiderably c:liiti~gcd. We have left 4.89$ of magnesia, ~ J . alumiiia K aiid 18.08lime, and then niaking the calculatioii we have : liypothetical Eirgli~h Slag. SItig.
Si0,-.-58.04 8i025Y.0', Si0,33.01- -54.00 ?JgO-.- 4.89 ': JlgO 4.89 or reducing 31gO 4.47-. 0.57 A1,0,-. 0.97 or A1,0,0.91 ;,to pels c a t . ~ 1 ~ 0 ~ 0 ..1H.04 88. 8bIgO=Cix1.40 11.20Ca0 ; CaO 46.97 (';LO 41.66. -25.67 1O d l 0, =1.631 X 10 16,31CaO , ___ - ___ 1OR. 49 100.00 .__ I
--
I f we compare this composition with that of the Eiiglish slag we find t h a t the two analyses are quite different, ;tiid still tliey represent t w o silicates of the s ; m e type, likely to be f o u n d in :L f u r nace uncler the same conditions of temperature arid iron. If: for t h e sake of illustration, we replace iii the original typical slag, 8% of magnesia and I S of lime by their equivtilents i n d i i w i i w .fool, s n t u ~ c c t i o wqf silicci we have the composition : IIypothetical Slag.
S i 0 2 58.04 SiO, MgO 4.8!) or reduciiig ilIg0 cito 0.08 to c!il(-)
Al,0,28.87
_-
'31.88
per ct.
EiigIisii slag.
SiO, :;1.00 >.Q? NgO 0.5; CaO ?5.0'; 0.09
(i3.16
Li1203 :{1.45
--
AlzO:3 13.0;
100.0.!
This is i~ perfectly iiezttrnl silicate, and certainly this composition does not correspond to t h a t of the Englisli slag. Xeitlier magnesia, lime, aluniiiia, or silica correspoiid, nor does the sum of tho bases, 38.8G, in o m ~ i s 1!):28 e ~ i;: tlie otlicr, offer mitlrnl any bases for a comparisoii. Still they are both ~~:uictZy slngs and t o all purposes, jndging from the type, would have the same fusibility, and would accompany the same grade of iron. T h i s is going to extremes, of course, in order to show how far t h e diflerences may be cliaracterietic. Heiice, I J i c appni*e7~tcomposit i o n qf n slay does ?tot uJ4bi-d any mentis qf c o i n p r i s o n iu certni?t cases niirl 710 sxre one i n nity cases.
BLAST F U R N A C E SLAGS, BTC.
211
It has occurred to thc writer, and he has used this method extensively in practice, that, instead of calculating the formule, slags could be readily compared in the following manner. Admitting t h a t slags are regular compounds, multiple silicates of the bases in RO and R,O, of the same type, or even taking their empirical formula without any hypothesis or admission on this point, i t is evident that, taking the saturation of the different bases for SiO,, as given in the preceding table for the different types, if we calculatp the proportional quantities of all the other enrthy elements as lime, and then reduce the composition thus found to pur. et. we can show all slags to be composed simply of silica n v d linie in various proportions for each, as the case may be. If we compare the numbers thus obtaiiied with the typical slags transformed in the same manner, we can ascertain a t a glance not only t o what type a given slag corresponds or between which types it falls, but also h o w d o s e to n given type it comes ; the percentage of i t s l‘baskity,” so to speak, and this, whatever may be t h e number or the nature of the bases entering into the composition of the silicate, since what has been said above regarding MgO and CaO will apply, with equal truth, to all the bases of the class RO, and, as regards A l t o 3 , to all bases OP the class R,O,. Referring to Table III. and transforming all of the bases into their equivalent in lime, and rcdticing to per. ct.; or, calculating directly from the f o r m u h RO, 2Si0, . CaO, 2Si0, (Table I.), we have : T S B L E V.
. .
--1.6071 1.0714 0.714 0.538 0.357 0.268 0.622 0.932 1.400 1.858 2.829 3.732
______-_.
lCaOsatni*ates SiO,*- 2.143 1Si0, ‘‘ C u O - . 0.466
212
I3LAF'C F C R S A C E SLAGS, ETC.
found exactly the same results a6 in Table V. o r , a t least, figurea a s uear to the above as the differences i i i the numbers expressing the old and uew equivalents of the same siibstaiice uould haye permitted ; iu fact, the hundredthe only are affected. a8 previoudy rcmarked. For inetance,the formula 2R0,Si02 (Bibnsic) C'orreeponds to SiO3 to 3RO. SiO,: the eqlii\ aleirt of lime \%'a&formerly taken as = 28.25, that of e i l i i i i UI 45.25. We ehmld h a \ ? had then for rhe silicate 3cii0, S O 3 : SCaO = 84.76 Liiiie 66.19 I~educiiipto per. rt.: H i O , = 45.25 SilicL, 31.81
__
-
1YO.00 100.00 With the corrected eqliivalent, 28.00,aud t h e new formula, 2H0,Silt,. n e have found :
i;y:i, 3":; 1 the differelice lieiiig only
iii
hlliidredtns.
100.00
Having a table of the equivalence i n lime of the different bases as far as saturation for silica is c>oncerned (Table 111. (a) ) the caiculations are very simple. Using this method, let 11s compare the typical neutral slag with the English slag of Percy mentioned above. T h e neutral slag corresponds to diu, 51.'72$, CaU 45.28 (Table V.) the English slag to and the composition of the slag is eqnivalent t o SiO, 54.00 SiO, 51.2'; CaO ,51.33 Or CaC) 48.73 105.33 100.00 S i 0 2 - - 5 4 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 54.00 h l , O , = .13 X 1.631-- _ _ - _ _ -31.25 CaO 7 ;MgO=O.57 X 1.40 _ _ _ _ _ _ _ _ _ 0.80 " i FeO=2.44 x 0.78 _ _ _ _ _ _ _ _ _ 1.90 ( ' 251.33 CaO. N n O = 2 . 2 0 X 0.78 _ _ _ _ _ _ _ _ _ 1.71 '' I CaO=25.67 _ _ _ _ _ .29.67 _ _" _j _ _ _ . . Compared with tlie type SiO, 51.71 CaO 48.28, the differences are as close as we can come, using two places of decimals in analyses. Both slags are neutral; 0 of acid : 0 of bases :: 3 : 1. T h e English slag actually run from a charcoal furnace was exactly the chemical compound having t h e formula RO, SiO, + H203,3Si02= (RO, R 2 0 3 , 4SiO,), the latter being the empirical formula. T h e first form supposes t h a t the silicates in, RO and R 2 0 , , are of t h e same type, and it is difficult to conceive bow it can be otherwise in a slag A slag is a
BLAST FURNACE SLAGS, ETC.
213
multiple silicate having a certain fueibility quite different from t h a t of the simple silicates which enter into its composition ; it must be then t h a t silica is so combined with all the bases as to form a compound ; having a definite constitution, which can be reproduced each time t h a t the different bases may be taken in t h e same proportion to each other and to the silica, each base saturating silica, according to its possible saturation in preseme of the others, in these conditions and this presence itself modifying the type. Any change in the quanitity of one of them-replacing a given weight of one by an cpzinl weight of another-(not a n equivalent weight as regards saturation for Si0,)-must necessarily give rise to another saturation, since the ratio of the quantity of oxygen of the SiO,, which has remained the same to the total amount of oxygen of the bases, which has been changed, is thereby modified. There exists, indeed, in relation to these combinations of oxygen compounds a law by which one can readily reach thc comparison of their analyses. T h e quantity of oxygen of one of the constituents, silica, is, in most minerals, a multiple or a sub-multiple of t h a t of the others. T h e determination of these numbers furnishes ratios which can be reduced to their simplest expression. By so doing there is n o hypothesis made as to the constitution of the substance, the results are furnished by the analysis itself, and i f the quantity of oxgen of the acid element, silica, is divided proportionately to the quantity of oxygen found to exist in the bases in 110 and to these in R,O,, and a rational formula deduced from the numbers t h u s calculated, it mill be found invariably t h a t the types of the silicates in RO and R,O, are the same and the same as that of the compound itself, regarded as a multiple compound in RO and B,O,. When in the analysis of a mineral the ratio of the quantities of oxygen can not be simplified, i t isalmost always to be attributed to the fact that these minerals have rarely crystalized alone, and t h a t in these conditions one of them may have carried with i t a certain quantity of other substances, as, when several salts are found together i l ~the same solution ; these foreign substances hide, so to speak, the real proportions, modifying to some extent the characteristic properties of the mineral. Nothing of the kind at any
rate can happen with a slag, consideriiig that its type as silicate is determined beforehand in tlie charges of a blast furnace, by furnisliing to the silica of ores, ston(J, a n d asli of coal, perfectly definite basic elements, in certain proportions primarily calci11at~?d, w 11i c 11 n ecessa r i I y d et e r m i 1 i e ii co i n po si ti 01i w 11 ic 11 t 11e u I ti mat e analysis of tlie s h g , as i - t i n from tlir. furnace, corroborates very closely in the great majorit1 of casr’s. \ V h r r i it does not hsppeti, it I M also to be attribute(1 t o clistur~)iiigfsctoi,s. :init tiley can be fountl, for instance, in this fact tiisit calciiitn, combined w i t h sulpliur, which the slags oftc>n wntitiii i i i very st’rious qaantities. has calculated :is oxide of ( ! ~ l ~ : i u i ioi r / i / w d , ‘L‘lic s:me ciin be said of magiiesiuni aiitl mangibtiesc. ci$ of sulpliur in a slag is by 110 metins :LII rsceptioiiiil circornstance ; S$ of inanganesc sulpliidt: is frequently inct with i i i Scotch slags. 111 otlier cases aluniiuii, owing t o certain condition of the furnace, or the proportions of flnses, w i l l play the par’t of a n acid, and, in these conditions, ouglit not to figure i n thc determinations of the type tis saturating silica. I x A e n
( T o De cvntinzcetl.)
T ) ~ ~ ’ l ’ E I ~ M I ~ A TOF IOK LI’l’HIA IS M I N E R A L WATERS. BY
E.
\vAI,I.EH.
1”.
1).
Practically, three methods are now available. 1. T h e phosphate method (Mayer’s modification) ( A t ~ i t C . h z . Q. Pharnz. 98, 193). 2 . T h c amylalcohol method (Gooch, Am. C‘hev). Jour., 9, 33). 3. T h e fluoride method ( C a ~ m tBur’/. , Soc. Chin). [3] 1, 280). Kammelsberg’s method (Poyg. Ann., 66, 79) somewhat similar in principle to that of (:oocli, in that it depends upon the comparatively greater solubility of lithium chloride in a n organic solvent, has been comparatively little used, on account of t h e difficulty and expense involved in obtaining the pure anhydrous alcohol and ether necessary for the process. Moreover t h e experiments of J. L. Smith ( A n , . Jour. Sci. [ 2 ] 16, 56), rearranged in convenient form for reference by Gooch (loc. c i f . ) do not indicate t h a t it is
