( 818 ) 
Chemistry. — “/nvestigations on the radium content of rocks.” IL. 
By Dr. E. H. Biicuner. (Communicated by Prof. A. Ff. HOLLEMAN). 
As a second contribution to the knowledge of the radium content 
of the earth’s crust,') I now wish to communicate the results of the 
measurements of a few sedimentary rocks. I may refer to my 
previous paper for particulars about the method of investigation ; 
only the way, in which the substance was brought into solution, 
may be briefly exposed. It was much shorter than in the case of 
igneous rocks, because the investigation has been limited to rocks 
which dissolve for the greater part in dilute hydrocbloric acid. | 
took, as usual, twenty-five grammes of the finely powdered rock 
and dissolved, gently heating, in 250 ee. dilute hydrochloric acid. A 
usually small residue was left, which, after having been separated 
from the solution, was fused with a little sodiaumearbonate. Leaching 
with water gave a solution, in which in all cases sulfuric acid could 
be detected. The presence of radium being hereby excluded, I rejected 
this liquid, and dissolved the very small residue of carbonates in a 
few drops of hydrochloric acid. This solution was mixed with the 
main solution, which then was measured in exactly the same manner 
as described in my previous paper. During the course of the measu- 
rements I have for the sake of security regauged the electroscope, using 
the radiumbromide solution of Professor Rutuerrorp; I obtained 
exactly the same value as formerly. 
The investigation concerns four samples of marble, six of limestone, 
chosen from different geological periods and one of chalk; fresh 
specimens of the rocks were supplied to me by Dr. F. Kranz of Bonn. 
The results are given in the following table, in which the figures 
relate to the quantity of radium per gramme of rock, expressed in 
10-2 grammes 
Marble: ot Tues iof Le te MTs et es 
Ps fo eh ioe SCO UN lende REDE 4 Sn 
\ ij ode. vaat shots ae Seer bach, IBereginasse... … „uk 
Ai NE Villa.” Nassaus cs. iy 
Limestone, ‘silurian, ~~). 09 Kuchelbad, (Prace, 200 
5 carboniferous. Ratingen, Düsseldorf . . 4,3 
ie EIS Ara MAREN Eek tE 
5 lias to & Varhingen, Wctembere: 2 
oy lower chalk . Egestorf, Hannover. . . 0,3 \ 
5 encene:.. oP Pars EN 0,8 
Chalk diluvial . . ….. -- Pietersberg, Maastmcht . … 1,5 
9) These Proceedings XIII, 359 (1910). 
