310 
POPULAR SCIENCE REVIEW. 
tion of iodine when in combination, proposed by Hempel and described 
by Mohr in his 11 Lehrbuch der Titrirmethode,” which under certain 
conditions cannot be carried out with the desired precision, from the 
fact of the liberated iodine giving a violet tint to the liquid. Briicke 
shows how his method can be advantageously made use of in this case. 
If any salts of cobalt happen to be present in a solution in which the 
amount of a constituent is to be determined by means of permanganate, 
their pink colour so closely resembles that of the diluted reagent that 
the point when oxidation is effected is difficult to arrive at; the use of 
the spectroscope, however, enables the operator to detect the moment 
when the reaction is complete. A pale red solution of a cobalt salt was 
prepared, and a portion diluted with water ; permanganate was then added 
to it till the tint closely resembled that of the other portion, except that the 
colour was very slightly more violet ; when placed before the spectroscope 
the difference was very marked, all the five lines being readily seen. 
— Journal fur praktische Chemie , lxxxviii., 486. 
Neptunium .— During the last seventeen years the beautiful method of 
spectrum analysis has been the means of identifying five new elementary 
bodies : caesium, rubidium, thallium, indium, and gallium. It is with no 
little interest that we find that the existence of another element, in this case 
also a metal, has been detected by the old and more difficult method of 
mineral analysis. Hermann, who published his first paper on minerals con- 
taining metals of the tantalum group a third of a century ago, has found a 
new metal, which he has named neptunium, in a specimem of a tantalite ” 
from Haddam, in Connecticut. His examination has shown the specimen 
to be not a mineral species, but a mixture of about equal amounts of colum- 
bite and ferro-ilmenite, both of which minerals occur in the granite of 
Haddam. The metallic acids contained in this specimen are present in the 
following proportions : — 
Ta 2 0 5 . 
= 32-39 
Nb 4 0, . 
. . = 36-79 
I1 4 0, . . 
= 24-52 
Np 4 0, . . 
= 6-30 
100-00 
The method adopted in separating the oxide of the new body rests on the 
inferior solubility of its soda-salt in boiling water. Neptunium appears to 
exhibit all the more important properties of the metals of the tantalum 
group, and evidently finds a place amongst them. From niobium and il- 
menium it is distinguished by the fact of its fluoride forming with soda an 
amorphous insoluble precipitate ; the other metals give crystalline precipi- 
tates, which dissolve in twenty-five parts of boiling water. It can be 
separated from tantalum by the property which its fluoride possesses of 
forming with potassium fluoride a salt which is easily soluble, the corres- 
ponding double compound of tantalum requiring 200 parts of water at 10° C. 
for its solution. The soda-salt of the new element colours a bead of micro- 
cosmic salt golden-yellow, while the other metals comport themselves under 
.similar circumstances in the following characteristic manner : tantalum, 
