Marcu 21, 1912| 
NATURE 69 
of radium chloride, that is, about four times the 
amount which has previously been available. He 
purified his salt by fractional crystallisation from 
dilute nitric acid, the method worked out by Mme. 
Curie. He took, however, certain precautions not 
taken by Mme. Curie, both in the purification and in 
the subsequent analysis by precipitation with silver 
nitrate. On the basis of 107-88 for silver, he arrives 
at the result 225-95, with a possible error of 0-02. 
Dr. Hénigschmid’s paper forms No. 7 of the 
Mitteilungen aus dem Institut fiir Radiumforschung, 
of Vienna. 
We have received a pamphlet containing an account 
of a new laboratory for experiments on radio-active 
substances which has been opened at Gif, Seine-et- 
Oise, under the direction of M. Jacques Danne, editor 
of Le Radium. The laboratory, which is private in 
character, has been arranged to provide facilities for 
commercial and scientific work on _ radio-active 
minerals and products, and to provide the necessary 
apparatus and instruction for those who wish to 
acquire a practical knowledge of radio-active methods 
and their application. In addition, it will be avail- 
able for investigation both in the theoretical and com- 
mercial side of radio-activity. The laboratory is con- 
veniently situated in a retired spot about 206 kilo- 
metres from Paris, and consists of a number of 
detached buildings, including a laboratory for 
chemical and physical work on radio-active sub- 
stances, another for research and practical instruc- 
tion, and also a library and administrative offices. 
Photographs are given of the various buildings and 
the interior of some of the laboratories, which appear 
to be well equipped for the work proposed. The 
laboratory has been designed to supplement the work 
of university laboratories and radium institutes, and 
no doubt will prove of value especially in connection 
with the commercial side of radio-activity. The 
creation of this laboratory illustrates the increasing 
technical as well as scientific importance of the 
rapidly growing subject of radio-activity. All com- 
munications are to be addressed to the director of the 
laboratory at Gif, or at his office, g1 Rue Denfert- 
Rochereau, Paris. 
As the result of their measurement of the expansion 
of mercury, Prof. Callendar and Mr. Moss in their 
recent paper before the Royal Society gave the value 
of the mean coefficient of dilatation between o° and 
100° C. as 182-05x10-°. As this result differs from 
the value 182-54 10-° obtained by Dr. Chappuis at 
the Bureau international des Poids et Mésures, they 
express the opinion that it is not safe to take the 
coefficient of cubical expansion of the material of a 
containing vessel as three times the linear coefficient, 
which Chappuis had done. In the Verhandlungen 
der Deutschen Physikalischen Gesellschaft for 
February 15 Drs. Scheel and Heuse, of the Reichs- 
anstalt, show that the results of Chappuis for both 
water and mercury agree with those obtained at the 
Reichsanstalt, and they are disposed to think that 
some error has crept into the measurements of 
Callendar and Moss. They support this view by 
reference to Harlow’s measurements of the expansion 
NO. 2212, VOL. 89| 
of fused silica. When these are based on the results 
of Callendar and Moss they differ from, and when 
based on the older results they agree with, those of 
other observers. 
Tur Bausch and Lomb Optical Company has for- 
warded to us specimens of their new and improved 
models of microscopes produced at the beginning of 
the present year. This American firm is well known 
for first-class work, and its association with the Carl 
Zeiss optical works at Jena, with which it exchanges 
ideas and experiments, gives it great opportunities 
and standing; the various improvements it has 
effected, together with reduction in prices, will there- 
fore be of interest to all users of the microscope. The 
type of instrument is Continental rather than British ; 
there is no centring of the substage for bright field 
illumination, although the dark field is provided for 
in this respect. We note the presence of provision 
for oblique illumination, the absence of which 
generally in our English stands is regretted by 
some. Messrs. Bausch and Lomb do not catalogue 
apochromatic objectives, but, as was to be expected, 
their association with the Jena glass works enables 
them to produce achromatics of excellent quality, 
penetration and minimum of colour being their 
characteristics. It is worthy of note that they obtain 
these results without using fluorite. Some of the 
smaller instruments are marvels of cheapness, and 
great choice of fittings is given. We direct special 
attention to the mechanical stage provided for fixing 
to a square stage; it is one of the cheapest and most 
convenient we have seen, the screws being in close 
juxtaposition. The pamphlet on the use and care of 
the microscope issued with each instrument is admir- 
ably written and is full of suggestions of value to the 
beginner. ; 
In continuation of their well-known experiments on 
photochemical action, Profs. Ciamician and Silber 
describe in the Atti dei Lincei (vol. xx., p. 673) a 
number of striking cases of oxidation of aromatic 
hydrocarbons brought about by sunlight and gaseous 
oxygen in presence of water. Toluene, the three 
xylenes, and cymene, when mixed with water and ex- 
posed in large flasks or bottles to the action of the 
gas in bright sunlight during several months, give 
rise to the corresponding carboxylic acids, toluene 
forming benzoic acid and the xylenes the correspond- 
ing toluic acids; the yield in some cases was as high 
as 30-40 per cent. of the theoretical quantity. Small 
quantities of the dicarboxylic acids are also formed 
in the case of the xylenes, metaxylene, for instance, 
yielding isophthalic acid. p-Cymene gave rise prin- 
cipally to paracumic acid, C,H,.C,H,.CO,H, but the 
interesting compound (CH,),C.(OH).C,H,.CO.H was 
also formed, together with its product of dehydration, 
C,H,.C,H,.CO,H. It is noteworthy that ortho- and 
para-nitrotoluenes: remain unchanged when exposed 
to the action of moist oxygen under similar condi- 
tions, without giving rise to more than traces of 
acid. 
A usEFUL addition is made to our knowledge of the 
strength of reinforced concrete piles in an article in 
Engineering for March 15. The author, Mr. EowEl 
