a i 
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DECEMBER 7, 1916] 
NATURE 
281 
. REFRACTORY MATERIALS. 
GENERAL discussion on refractory materials | 
was held.on: November 8 at the Faraday Society, 
the chair being occupied by the president, Sir Robert 
Hadfield. Numerous exhibits were on view, including 
British, Colonial, and Indian raw materials, manu- 
factured products, appliances, etc. 
In his introductory address the president surveyed 
the whole range of refractory materials, and mentioned 
that when Belgian sand was no longer available for 
open-hearth furnace bottoms, those concerned were not 
long in discovering British sands which~ give prac- 
tically the same results. This point was emphasised 
later by Mr. Cosmo Johns and Dr. Boswell. 
Dr. J. W. Mellor (Stoke-on-Trent) opened the dis- 
cussion with a paper on S 
“The Texture of Firebricks.” 
Dr. Mellor classed texture and refractoriness as the 
two most important properties, of a firebrick. Numer- 
ous samples illustrating texture were exhibited, pre- 
pared by cutting across with a saw, polishing the cut 
face, and cementing a glass plate on with hot Canada 
balsam. This method of showing a brick’s texture 
(now used, it is believed, for the first time) was sug- 
gested by Mr. Lomax. 
Size of Grain. 
| The softening of clay material takes place gradually. 
From the fact that increased fineness of grain has been 
found to increase the contraction of fired clay bodies, 
presumably owing to increased surface reaction in 
promoting vitrification, it might be expected that pres- 
sure would also lower the softening temperature of a 
clay by increasing the: area of contact, and this has 
recently been shown to be the case.? 
This effect of fineness ot grain comes out promin- 
ently in the case of high-temperature fluxes, like mix- 
tures of clay and fine-grained quartz, where the vitrifi- 
cation temperature may be brought so low as to spoil 
the firebrick. Conversely, the presence of coarse- 
grained quartz appreciably increases the refractoriness 
of fireclays; the quartz grains, however, should be 
angular, not rounded, the rounded quartz grains being 
only loosely held by the clay bind, besides which angu- 
lar particles pack together more closely and form.a 
more compact skeleton for the brick, as in samples 
exhibited. . 
After-Contraction and After-Expansion. 
The firebrick manufacturer arrests the chemical re- 
action at a certain stage. When the brick in use is 
strongly heated, the uncompleted reaction is continued, 
giving rise to after-contraction. This after-contraction 
a few years ago amounted to 2 or 3 per cent., but was 
reduced by improved methods to 1 per ¢cent., and then 
to 3 per cent. It is usually impracticable to eliminate 
all the after-contraction in the original burning of the 
firebrick.* Silica firebricks show an after-expansion, 
which may reach up to 16 per cent. The quartzose 
silica of clays behaves similarly, unless it be dissolved 
by the fluxes. The fluxes in a clay also expand about 
6 per cent. in firing, so that the apparent contraction 
of a firebrick is a joint effect. In silica bricks the 
resultant effect is an expansion. 
Refractoriness and other Qualities. 
It is clear that conditions which increase the extent 
of surface of the clay particles in contact or which 
produce closer contact make the clay soften at a lower 
temperature, and this indicates how to obtain maxi- 
mum refractoriness for normal conditions with a given 
1 J. W. Mellor and B. J. Moore, Trans. Eng. Cer. Soc., xv., 117, 1916. 
NO. 2458, VOL. 98] 
SE ee ee —————— 
clay. The refractoriness can be further augmented by 
addition.of some of the higher refractories, like shrunk 
bauxite, shrunk zirconia, or carborundum. It should, 
however, be borne in mind that a coarse-grained re- 
fractory material has low crushing strength and 
tenacity, and is also very friable and liable to dis- 
integration by shocks or abrasion, besides being easily 
penetrated by flue dusts and slags. When maximum 
refractoriness is not really wanted, some refractoriness 
may be sacrificed advantageously to improve other 
desirable qualities. 
Hand-made v. Machine-made Iirebricks. 
With reference to the making of firebricks by hand 
or by machinery, the machines often get blamed for 
faults which have no direct connection with the use 
of the machines, but arise from differences in. the _ 
method of preparing the clay, which affect the 
uniformity in texture of the product. 
Corrosion of Firebricks, 
The joints between firebrieks are the weakest places 
in a structure. Where slags are concerned. the fire- 
bricks should be fine-grained, and the jointing clay 
should quickly vitrify without cracking and weld the 
bricks together when the furnace is fired for the first 
time. Where bricks are exposed to corrosive vapours 
the chemical composition is of special importance, as 
well as the texture of the bricks. 
Prof. T. Turner (Birmingham), referring to Dr. 
Mellor’s statement that angular particles give closer 
packing than round particles, contended that the. 
closest packing of all is obtained by adjusting two 
sizes of round particles so that the smaller grains shall 
approximately fill up the interspaces between the larger 
grains, 
Other Refractory Materials. 
Dr. Hutton directed attention to the great value as 
refractories of completely: shrunk silica, alumina, and 
magnesia, all of which can stand sudden heating and 
cooling. 
Dr. W. Rosenhain stated that zirconia has a pro- 
mising future as a refractory material, especially the 
purified substance. It withstands very high tempera- 
tures, but should be previously heated to a higher 
temperature than that to which it is to be exposed, in 
order to avoid cracking. It is also very apt to form 
a carbide in a reducing atmosphere, and the properties 
of the carbide are very different from those of the 
oxide. J. A. A: 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
Liverroot.—The University has just received two 
valuable gifts—Soool. from Mr. C. Sydney Jones, to 
endow the chair of. classical archeology, hitherto 
maintained by temporary guarantees, and 10,0o0l. from 
Prof. and Mrs.. Herdman, to establish a chair of 
geology. Both chairs are memorials: the first of.a 
father, Mr. Charles W. Jones; the second of a son, 
Lieut. George A. Herdman, a young student, not 
merely of promise, but of distinction, who was killed 
in action in France a few months, ago. . Each satisfies 
a real need, for at Liverpool the course of study in 
Latin and in Greek recognises that without some 
knowledge of life and. custom it is impossible to 
understand ancient history or to appreciate: classical 
literature. The professor of classical archzology, 
therefore, takes an active part throughout the classical 
course, though his worl: is so arranged as to leave 
one term in’the session free for research at home or 
abroad. 
