IN RELATION TO QUANTITATIVE CHEMICAL ANALYSIS. 
339 
corresponding to wave-length 2250 being liable to be confounded with the copper lines 
at the same point, and one of the less refrangible lines of silver being also liable to con¬ 
fusion with a group of copper lines with wave-lengths lying between 3245 and 3310. 
Referring to the table we get the exact wave-lengths of the lines and their position on 
the scale, so that they may be identified at once on a photographed prismatic spectrum. 
A similar reference to the silver and lead maps and tables will at once tell us the 
exact position of those lines which are to be sought for in a specimen of argentiferous 
lead. In very many cases the character of the lines is sufficient to identify them, 
provided we know something of their position. It may not be without interest if a 
description of the method of working which I have adopted be made to serve as the 
conclusion of this portion of the paper. 
An estimation of beryllium. —A preparation of ceric phosphate was examined in 
order to establish beyond all doubt that it was of great purity. A 10 per cent, 
solution of the substance in hydrochloric acid yielded photographs in which none but 
cerium lines were visible, with the exception of one single line with a wave-length 
3130‘2 belonging to beryllium. A solution of beryllium oxide containing nmoll 1 of 
the metal was diluted to 100 times its original volume before its spectrum was com¬ 
parable with that of the ceric phosphate. It was then seen that the line with the 
wave-length 3130'2 was much stronger than in the photograph of the ceric phosphate. 
It was therefore considered proved that the preparation contained less than 0‘01 per 
cent, of beryllium. 
The analysis of an amygdaloid limestone. —The complete qualitative and quanti¬ 
tative analysis of a mineral as far as regards the bases present was carried out in the 
following manner. The substance, which we will call mineral (a), consisted of small 
almond-shaped masses apparently of the nature of zeolites interspersed with a highly 
crystalline and almost transparent material considered t© be the matrix. It effervesced 
with acids, dissolving completely and yielding no residue of silica, a result which was 
quite unexpected. After evaporation to dryness, twice repeated, there was even then 
no appreciable quantity of silica. A strong solution containing 20 per cent, of the 
solid was submitted to the spectroscope; the calcium lines came out prominently in 
the photograph, and in addition the quadruple and the quintuple groups of magnesium 
were noticeable, but no other metallic lines. Magnesium being in much the smaller 
proportion was estimated first. 
The estimation of magnesium. —One gram of the mineral was dissolved in hydro¬ 
chloric acid and made up to 100 centims. by volume. The solution yielded a spectrum 
with closest possible resemblance to that on the test-plate rendered by a solution 
containing ro .o ooth °f the metal. Three separate solutions were made containing 
1, 2, and 3 parts of the mineral in 1000 volumes of the solution. These were photo¬ 
graphed on one plate. On comparison with the standard photographs it was found 
that they exactly corresponded to those obtained from solutions containing 1, 2, and 3 
2x2 
