486 
NATURE 
[JuLy 11, 1912 
We have received from Messrs. Ozonair, Ltd., 96 | bromoform or ethylene bromide, which gives normal 
Victoria Street, Westminster, London, S.W., a copy 
of their catalogue of Ozonair portable generators for 
purifying the air in rooms of from 3000 to 12,000 
cubic feet capacity, the current being derived from 
the supply circuits or from portable accumulators. 
As the consumption of power is only from 10 to 130 
watts, the apparatus can be connected to any lamp- 
holder or plug. The makers claim that their appa- 
ratus generates ozone which is practically free from 
oxides of nitrogen. 
Tue French Société de Chimie-physique is publish- 
ing a series of monographs or lectures upon impor- 
tant topics in physical chemistry. Two of these, by 
Prof. Arrhenius, ‘‘Sur les atmosphéres des plancétes,”’ 
and by Prof. Gaubert, ‘‘ Recherches récentes sur la 
formation et le facies des cristaux,’’ were issued in 
igi1; two further issues have just come to hand. 
These include a series of lectures on alloys by Messrs. 
Rengade, Jolibois, and Broniewski, and a lecture on 
“‘La pression osmotique et le mécanisme de l’osmose,” 
by M. Pierre Girard. The lectures on alloys deal 
with thermal analysis and microscopic metallography, 
chemical methods applied to the study of alloys, and 
the relationship between the structure of alloys and 
their electrical properties. The lecture on osmotic 
pressure forms a valuable historical and critical re- 
view of the theory of osmotic pressure. 
Ir is often a tedious process to obtain sulphuric 
acid of the necessary degree of purity for detecting 
or estimating minute traces of arsenic. In the 
Gazzetta Chimica Italiana (vol. xlii., i., 456) a simple 
process is described by G. Bressanin for this purpose. 
It consists in adding ro c.c. of a 30 per cent. solution 
of hydriodic acid to a litre of the sulphuric acid, 
diluted to 50° Bé., leaving for twelve hours for the 
arsenic to separate, together with other metals, such 
as lead, tin, and copper, filtering through glass wool 
covered with a thin layer of asbestos, and finally 
boiling in a Jena glass vessel to expel the iodine 
liberated. 
Unper the title, ‘Solid Solutions of Iodine in 
certain Cyclic Hydrocarbons,’’ some interesting ob- 
servations are recorded by G. Bruni and M. Amadori 
in the Gazzetta Chimica Italiana (vol. xlii., p. 121), 
It has been known for some years that iodine gives 
abnormally high values for the molecular weight 
determined by the cryoscopic method, using benzene 
as solvent, and Beckmann concluded that this was 
due to some of the iodine separating with the con- 
gealing solvent in the form of a solid solution. In 
the paper now cited it is shown that cyclohexane, 
C,H,., which Mascarelli in 1907 found to form solid 
solutions with benzene, behaves cryoscopically with 
iodine exactly in the same way as benzene itself, 
giving values ranging from 310 to 320 for the mole- 
cular weight of iodine instead of 254, calculated for 
I,. When a very dilute solution of iodine in benzene 
or cyclohexane is cooled in carbon dioxide snow, the 
colour of the solution is scarcely changed at all on 
solidification owing to the formation of the solid 
solution; whereas, with an ordinary solvent, such as 
No. 2228, vol. 89] 
values for the molecular weight, on solidification the 
reddish-violet colour disappears to give place to an 
Opaque-greyish appearance, due to minute solid par- 
ticles of free iodine separating. 
SEVERAL important papers in the series dealing with 
water supply have recently been issued by the United 
States Geological Survey. They deal with the 
basin of the Missouri, with the lower basin of the 
Mississippi, with the rivers draining to the western 
Gulf of Mexico, and with California. It is pointed 
out in the general introduction to these papers that 
it is necessary to apply the money appropriated for 
the work over a wider field than it would be if only 
the scientific value of the work were under con- 
sideration. The appropriations made by Congress are 
applicable to all parts of the country, and each part 
demands its proportionate share of the benefits. It 
has been found, nevertheless, that the work of the 
Survey in this direction is of great practical value. 
Records have been obtained at nearly 2000 different 
points in the United States, including the reading 
of gauges, the measurements of discharge, precipita- 
tion, evaporation, reservoirs, river profiles, and water 
power, and some investigations have been made also 
in Alaska and Hawaii. In a special report on the 
Antelope valley of California, an interesting review is 
given of the manner in which land was taken up there 
in the early "eighties without any knowledge of the 
available water supplies, how many farms failed in 
consequence, and even towns were left derelict, and 
how part of the country has subsequently been brought 
under cultivation by means of a careful system of 
irrigation. 
OUR ASTRONOMICAL COLUMN. 
MAGNITUDE OBSERVATIONS aT HaRVARD COLLEGE 
OBSERVATORY.—An important contribution to stellar 
photometry is published in Circular No. 170 of the 
Harvard College Observatory, where Prof. Picker- 
ing gives the adopted magnitudes of ninety-six stars 
measured in the Harvard polar sequences. The first 
table gives the magnitudes of forty-six stars in the 
north polar sequence, the second the magnitudes of 
twelve stars in the N.P. sequence of red stars, and 
the third the magnitudes of thirty-eight supplementary 
standard stars near the north pole. Having had 
access to a large number of plates taken with different 
instruments, e.g. the 60-inch reflector at Mount Wil- 
son, Prof. Pickering is able to give magnitudes down 
to the twenty-first; on a plate accompanying the 
circular an excellent photograph taken with the 60- 
inch reflector, and showing the stars near the north 
pole, is reproduced. 
The periods of twenty-two variable stars are given 
in the same circular, with some interesting notes 
concerning the variations, in some cases irregular, 
and their connection with possible changes in the 
spectra. 
In Circular 172, Prof. Pickering shows that amateur 
observers might perform valuable service to astronomy 
by observing the photographic magnitudes of asteroids 
and gives lists of suitable asteroids and data concern- 
ing them for the current year. The variability of 
polaris is discussed, from the Harvard observations, 
in Circular No. 174, and a light-curve showing the 
nature of the changes is given. 
