366 REPORT—1846. 
The surface of this slag is covered with bright black crystals, exhibiting 
occasionally an iridescent tarnish. The crystals belong to the prismatic 
system. The normals to the faces make the following angles with each 
other :—n 2! = 49° 24', nt = 65° 18’, kk! = 98° 24', ht = 40° 48’. They 
cleave readily parallel to a plane p, which is perpendicular to the faces 
t,n,n', and makes equal angles with the faces f, h'. 
Hardness = 6. At 186 C. specific gravity of slag 
specific gravity of water 
fT 
= 4°0805. 
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13. AnaLysis. By J. P. 
This slag was found to contain silica, protoxide and sesquioxide of iron, 
protoxide of manganese, alumina, lime, magnesia, sulphur as sulphuret, and 
phosphoric acid. It was decomposed by long digestion with dilute hydro- 
chloric acid. The silica, however, obtained by this means was more or less 
gray; and in order to obtain it perfectly white, it was fused with the car- 
bonate of potass-soda mixture, and the fused mass, which had a bluish-green 
colour, was decomposed with hydrochloric acid. The solution was treated 
with nitric acid to peroxidize the iron ; ammonia was then added in slight 
excess, and the analysis continued in the manner formerly described. The 
proportion of the two oxides of iron, the phosphoric acid and the sulphur, 
were determined by separate analyses, as will be described in the sequel. 
1. Weight of slag 20°20 grains, after drying in vacuo over SO8 during 48 
hours. 
2. Silica 5°98. Repeated by Mr. Forbes; 20:14 grains of slag gave 5:99. 
3. Total amount of iron obtained as Fe? O3, 14°63. The oxide of iron 
contained a minute quantity of P?O°, which was not removed by boiling 
with potass; for on redissolving the iron in hydrochloric acid, adding excess 
of tartaric acid and afterwards excess of ammonia, and lastly, chloride of 
magnesium, a few minute crystalline grains appeared after standing some days. 
However, this error of excess must be very small. 
4. Oxide of manganese 0°256. 
5, Alumina 0°53. As the alumina was precipitated from its solution in 
presence of P? O°, and as only a minute quantity of this acid was retained by 
the iron, the whole amount of P? O05 may be subtracted from the alumina. 
The total P? O° obtained (vide sequel) was 1°34 per cent. 
20:2 (slag) : 0°53 :: 100 : 2°62. 
2°62 — 1:34 = 1:28 alumina. 
Taking the phosphate alumina as 4Al*O%, 3P205 (see Rappert Annuel, 
