1817.) during the Year 1816. 31 
is composed of 100 mercury + 16 sulphur, or of 1 atom mercury 
+ 2 atoms sulphur. (Ann. de Chim. et Phys. i. 422.) 
5. Steel. rom the statements of Dobeieiner and Goethe it 
would appear that iron is much better fitted for being converted into 
steel, when it contains manganese. (See Schweigger’s Journal, 
xvi. 102.) The substance noticed by Dobereiner in the place just 
quoted, I consider as the crystallized body occasionally found in 
hollows of cast-iron, and known in this country by the name of 
geess. Dr, Wollaston informs, me that he has examined this sub- 
stance, and that he found it a carburet of manganese. 
6. /ron.—In the Annals, vii. 320, I have given the result of an 
experiment lately made to determine the strength of British iron. 
It appears that an iron wire one inch in diameter is broken by a 
weight of 25:6 tons. Supposing Count Sickingen’s experiments 
correct, the strength of Swedish and British iron is to each other 
as follows :— 
PIA BOR ie'e' 5 OLDS oS. PU S4B'SS 
Swedish irony i 28. COT wks Cd DAM DS 
7. Peroxide of Lead.—Grindel has observed that when to a mix- 
ture of brown oxide of lead and sulphur a little phosphorus is 
added, and the mixture triturated in a mortar, a loud explosion 
takes place. (Schweigger’s Journal, xv. 478.) 
8. Oxides of Iron ——The general opinion at present entertained 
hy chemists, is that iron combines only with two doses of oxygen, 
forming two oxides, the black and the red; that the black is com- 
posed of 100 iron + 30 oxygen, and the red of 100 iron + 45 
oxygen. But this opinion is attended with some difficulties. When 
we compare the proportion of acid which combines with the black 
oxide with what unites with other salifiable bases, we find ourselves 
obliged to consider it asa protoxide. But in that case the red oxide 
presents the anomaly of one atom of iron combined with 1+ atom 
of oxygen, unless we consider it as a compound of 2 atoms iron + 
3 atoms oxygen. Gay-Lussac conceives that a third oxide of iron 
exists intermediate between the black and the red, and composed of 
100 iron + 38 oxygen. It is formed by passing a current of steam 
over red-hot iron. (Ann. de Chim. et Phys. i. 33.) Were we to 
admit the existence of this oxide, it would be necessary to consider 
the weight of an atom of iron as 13°46, The black oxide would be 
composed of 1 atom iron + 4 atoms oxygen, the new oxide of 1 
atom iron + 5 atoms oxygen, and the red oxide of 1 atom iron + 
6 atoms oxygen, But this opinion is not very probable. I am 
more inclined to adopt the opinion of Berzelius, who considers the 
new oxide of Gay-Lussac as a compound of the black and the red 
oxide. 
Gay-Lussac has shown by experiment that iron has the property 
of decomposing water at all temperatures up to a white heat, and 
that hydrogen in the same circumstances decomposes the oxide of 
iron, This constitutes an anomaly in the received doctrine of 
