432 
with the compounds Pb,Si,0, and PbSiO;, re- 
spectively. It is interesting that the artificial 
alamosite was prepared and characterized before 
its counterpart was found in nature. The crystal- 
lized lead silicate formations found under dis- 
mantled smelters are rather miscellaneous in char- 
acter, the largest crystals being of mixed com- 
position. 
H. S. Fry: Some Application of the Electronic 
Conception of Positive and Negative Valencies: 
V. Dynamic Formule and Absorption Spectra 
of Chlor- and Brom-benzenes. 
F. D. Wiuson: A Further Study of the Action 
of Calcium Carbonate on Zine Sulphate Solu- 
tions. 
When calcium carbonate and zine sulphate solu- 
tions are brought into contact with one another 
in varying preparations, and at different tempera- 
tures, and for different periods of time, the basic 
carbonate is formed. 
When the solution of zine sulphate is changed 
into carbon dioxide, and calcium carbonate added, 
and carbon dioxide passed in for several days, 
the normal carbonate of zine with from 0.8 to 
1.5 per cent. of water is formed. 
RoBert B. Sosman: The Nitrogen Scale from 300 
to 600 Degrees. 
CHARLES BASKERVILLE and ABRAHAM LUSSKIN: 
Chemical Tests for Lanthanum. 
As far as we are aware, there are no chemical 
tests for lanthanum which are so distinctly char- 
acteristic as to be used to prove the presence of 
that element when associated in mixtures with 
neodymium or praseodymium. Recourse must be 
had to photographic reproduction of the are or 
spark spectrum, facilities for which do not consti- 
tute a part of the armamentarium of all analytical 
chemists, and at best this is not applicable upon a 
quantitatively qualitative basis. 
Having exhausted the probabilities of analogous 
tests for other metals, recourse was had to the 
empiricism offered by a Kahlbaum catalogue. 
While much not recorded in the literature was 
observed as to the conduct of this subgroup of the 
so-called rare earths with many unusual reagents, 
the main object was to secure some one or more 
definitely distinctive tests for lanthanum alone or 
in mixtures. While it may be stated that results 
altogether satisfactory were not obtained, the fol- 
lowing may be noted. 
Conduct with Sodiwm Potassium Tartrate.— 
Solutions of lanthanum, neodymium and prase- 
odymium salts, singly or mixed with each other, 
SCIENCE 
[N.S. Vou. XXXV. No. 898 
give precipitates with this reagent which dissolve 
in an excess of the precipitant. On adding oxalic 
acid to these solutions a precipitate is produced in 
each case, but with lanthanum the precipitate is 
soluble in excess. Filtration, evaporation and 
ignition yield lanthanum oxide. The delicacy of 
the reaction and all the determining factors have 
not been established. 
Conduct with Cyanates——Potassium cyanate 
gives a white gelatinous precipitate insoluble in 
excess. On standing the precipitate changes into 
beautiful silk-white crystals. Similar conduct was 
observed with neodymium and praseodymium salts, 
except that each of the latter exhibited the char- 
acteristic rose or light green tint. The solubility 
of these cyanates, the composition of which has 
not been determined, was investigated, using a — 
great variety of solvents, some very unusual. A 
difference was noted in the solubility in bromine 
water, the lanthanum salt being more soluble. In 
acetic acid, however, the lanthanum salt dissolved 
much more slowly. The same was noted with lactic 
and phthalic acids and boiling sodium tartrate 
solutions. In the last the neodymium preparation 
is entirely soluble, whereas the lanthanum salt is 
only slightly, but appreciably, soluble. 
Neither of the methods has so far shown itself 
suitable either for satisfactory qualitative pur- 
poses or for separating lanthanum from the 
didymium on a laboratory scale. 
Suggestions as to rarely applied tests will be 
most acceptable. 
CHARLES BASKERVILLE: On 
Praseodymium. 
The results of twelve years’ study of prase- 
odymium with different assisting workers in an 
effort to show its complexity are given. All efforts 
to decompose praseodymium were unsuccessful. 
The investigations were carried out along the fol- 
lowing lines: (1) fractional precipitation from 
salt solutions; (2) fractional solution of the black 
oxide in acids; (3) fractional decomposition of 
the nitrate by heat; (4) fractional crystallization 
of double nitrates, one being an isomorphous ni- 
trate of another metal; (5) fractional oxidation 
of a soluble salt of praseodymium; (6) fractional 
oxidation of the oxide by fusion with an alkali 
peroxide, and (7) fractional electrolysis, with and 
without a porous cell. The absorption spectrum 
of the different fractions, several thousand all 
told, was taken as a criterion as to any disintegra- 
tion. Solutions of a definite strength, acidity and 
thickness were compared. 
the Simplicity of 
