APRIL 18, 1912] 
NATURE 
177 
PORTLAND CEMENT. 
M LEDUC has made a notable contribution to the 
* literature of a subject which already possesses 
matériel more remarkable for quantity than merit, 
and, departing from topical traditions, has given us 
many useful data with tew speculations. 
An excellent historical preamble is succeeded by a | 
description of the methods which he employed in his 
endeavour to throw light on the constitution of cement 
—~a question which is taxing, and will continue to 
tax, the best efforts of the chemist, equipped as he 
must be with ample knowle’Ze of physical methods 
of research. Provision of a suitable apparatus for 
working at high temperatures with relatively large 
quantities of material, say a couple of kilogrammes, 
needed much thought and many trials, and was 
attained by the device of a furnace heated by three 
burners fed with gas and air under pressure, these 
playing below the hearth on which the test pieces are 
placed and the gases being deflected back above the 
hearth before reaching the flue, so that as uniform 
a temperature as could be expected from any con- 
trivance heated by fuel was secured. In many in- 
stances of this sort where the experimenter finds him- 
self in a difficulty useful recourse may be had to some 
industrial apparatus, and M. Leduc, fully alive to 
this, used one originating with a famous firm of 
motor manufacturers, and records the result with a 
touch of sadness :—‘‘Enfin, dans un essai qui, mal- 
heureusement, s’est terminé par la fusion compléte 
et le mélange d’un grand nombre d’échantillons, j’ai 
utilisé le four a porcelaine dure de la maison de 
Dion-Bouton, que M. Guillet, professeur au Conserva- 
toire des Arts et Métiers, avait bien voulu mettre 
& ma disposition.” 
The author prepared the first of the calcium silicates 
which may occur from the interaction of cement raw 
materials, that is, wollastonite, CaOSiO,, and notes 
in passing that the product had a pale-green tint, 
which he attributes to the presence of a trace of iron. 
Seeing that the silicate is relatively acid, the reviewer 
would not care to contest this explanation, but he 
would point out when white Portland cement, neces- 
sarily a far more basic material, is made from the 
purest materials obtainable in commerce as distinct 
from strictly laboratory products, it also possesses a 
pale-green tint, and that this tint is due, not to iron, 
but to manganese, probably present as calcium man- 
ganate. Dicalcium silicate, that is, the orthosilicate, 
2CaOSiO., was also made with ease, as other experi- 
menters have established; but, again confirming 
earlier results, the preparation of that illusive body 
3CaOSiO, proved to be impracticable. So far as we 
know, the only successful attempts have been those 
of Le Chatelier some twenty-five years ago, in which 
not pure 3CaOSiO, but a body in which part of the 
CaO is replaced by CaCl, was prepared, and the 
recent work of Shepherd and his collaborators, who 
have shown that tricalcium silicate has a small range 
of stability in respect of temperature, and it is in 
consequence of this that its existence as an individual 
substance has been so much and so justly doubted. 
M. Ledue’s conclusions are such that we will quote 
them without fear of the accusation of laziness 
properly levelled at commentators on other men’s 
work. 
CaOSiO, has no hydraulic properties; neither has 
2CaOSiO,, which can only be made in the dry way, 
and is decomposed by water into the monocalcium 
silicate and lime. 3CaOSiO, has not been prepared. 
CaOAl,O, and 2CaOAl,O, are hydraulic and stable | 
in hot water. 3CaOAl,O, has not been obtained. | 
1 “Sur Ja constitution et la formation du ciment Portland.” By E. 
Leduc. Bull. Soc. d’Encouragement, Paris, November, rort. 
NO. 2216, VOL. 89] 
| The calcium-ferrites are not hydraulic, and no silico 
| aluminates or silico-ferrites containing a high per- 
centage of lime could be prepared, the products tall- 
| ing to powder on cooling in the manner characteristic 
of dicalcium silicate. 
Concerning commercial cements, the fact recognised 
in practice, that the mechanical strength falls off 
rapidly as the content of clay is increased, is con- 
firmed, and it is also shown that the coarseness of 
grain of both clayey matter and of sand has at least 
as large an influence on the “falling” of clinker as 
| has the amount of their constituents. A normal 
clinkering temperature is set down at 1400-1450° C. 
Cements in which the alumina is replaced by ferric 
oxide are mechanically weak, and those containing 
considerable quantities of magnesia, e.g. 25 per cent., 
went to pieces when exposed to steam. It should be 
noted that M. Leduc took unusual pains to bring his 
raw materials to an extremely fine state of division, 
fully comprehending that in a mass which is almost 
plastic the occurrence and completion of the reactions 
concerned in the production of definite silicates, 
aluminates, and the like are dependent on the intimacy 
of admixture, as well as on the temperature and the 
time. Anyone who has prepared Portland cement 
experimentally knows that particles of sand which 
may be only 1/10 mm. in diameter will each produce 
its small centre of “falling,” the dicalcium silicate 
oozing forth from the site of the grain in a very 
curious lifelike and vermiform manner, whereas the 
same raw materials, really finely ground, will not 
“fall” at all. 
One more word, and we will close an appreciation 
of good work well done. M. Leduc has shown, in 
collaboration with M. Chenu, that Seger cones, useful 
as they are for many industrial purposes, are far from 
exact as indicators of temperature. They may well be 
used side by side with materials of the same class 
which are to be heated in the same way, but in all 
cases they must be checked by whatever kind of pyro- 
meter is best adapted for the temperatures to be 
measured. Failing this the most careful inquiry may 
be misleading. Boe 
| 
PLAGUE IN INDIA. 
HE sixth report on plague investigations in 
India, which, like preceding reports, has this 
year been issued as a supplement to The Journal of 
Hygiene, is in large part made up of a continuation 
by Dr. M. Greenwood of the statistical examination 
of plague as it occurs in the Punjab. In the applica- 
tion of statistical methods to a subject-matter so 
complex it is a considerable advantage to the in- 
vestigator to have himself personal experience of the 
methods, particular conditions, and so on affecting 
the collection of the data with which he has to deal, 
and adds cogency not so much to the facts elucidated 
as to the conclusions based upon these facts. It is 
particularly unfortunate, therefore, that the death of 
Major Lamb deprived Dr. Greenwood of the assist- 
ance which his wide experience and knowledge of 
local circumstances would have afforded. Major 
Lamb, of whom a memoir is included in the report, 
was one of the most brilliant members of the Indian 
Medical Service, and his untimely death in this 
country has taken from plague research in India one 
of the ablest, keenest, and at the same time best- 
informed of its students. ; 
In the Punjab cases of plague continue to occur, 
though in reduced numbers, during the off-season, 
and this persistence is met with chiefly in the larger 
villages. Dr. Greenwood’s first paper is a contribu- 
tion to’ the question whether in the smaller villages 
