TRANSACTIONS OF THE SECTIONS. 35 



exactly like an organic analysis, and is the method invented by Regnault. An im- 

 portant point in the determination of the carbon in iron is to ascertain the propor- 

 tion of carbon in a state of combination, in contradistinction to that •which is 

 mechanically mixed with the metal. Dr. Bromeis effected this by dissolving the 

 mixture in muriatic acid ; the carbon in chemical combination unites with hydrogen 

 and forms carburetted hydrogen, while the carbon in mechanical mixture takes no 

 part in the action, but remains unaffected, and may be accurately determined. This 

 quantity, being subtracted from the whole carbon obtained by combustion, affords a 

 means of estimating the quantity in chemical combination. 



Dr. Bromeis found in crystalline white cast iron, 3 '8 per cent, of carbon ; but as 

 some white cast iron has been found to contain 4% or even 5"3 per cent., Dr. Bromeis 

 considers that manganese may be substituted for it ; he sometimes found as much 

 as 7 per cent, of this metal. It appears, therefore, that neither common nor white 

 cast iron are polycarburets of determinate constitution. 



In white cast iron Dr. Bromeis found only 0"5 per cent, of mechanically combined 

 carbon, in other kinds nearly 1 per cent., and in gray cast iron 2'3 per cent. Hence 

 it follows that the chemically combined carbon amounts only to 0*9 per cent. Kars- 

 ten found 0'85 per cent. 



Cast steel, according to Gay-Lussac and Wilson, contains - 93 per cent, carbon. 

 Bromeis found in hard cast steel, 0'97 per cent. 



Gray cast iron may be considered as a mixture of very impure cast steel with 

 carbon. This may possibly be the cause that it can be so easily hardened on the 

 surface. 



On Kakodylic Acid and the Sulphurets of Kakodyl. By Prof. Bunsen 

 of Marburg. 



In the present paper Prof. Bunsen examines the higher stages of oxidation of 

 kakodyl, and the sulphurets corresponding to them. He finds that by the oxidation 

 of alkarsin, either by the direct action of the air or by means of oxide of mercury, 

 kakodylic acid is formed ; but there is also an intermediate oxide which cannot be 

 obtained in a state of purity, which seems to be similar to the hyponitric acid, and 

 to be a combination of kakodylic acid with the oxide. Kakodylic acid crystallizes 

 out of alcohol ; its composition is C 4 H 6 As 2 O 3 -f H O, this atom of water being 

 constitutional, and only to be replaced by a base ; it is soluble in water but not in 

 aether. A very remarkable fact with respect to this body is, that the poisonous pro- 

 perties of the arsenic seem totally annihilated ; eight grains administered to a rabbit 

 exerted no poisonous action. 



Kakodyl combines directly with sulphur, forming the protosulphuret which has 

 been already described. This compound takes up another atom of sulphur, and 

 produces the bisulphuret. There appears also to be a tersulphuret analogous to 

 kakodylic acid. Prof. Bunsen has not, however, been able to obtain it in a pure 

 state. From the above results, it appears that kakodyl is precisely similar in its 

 behaviour to some simple metals ; and the formation of kakodylic acid by direct 

 oxidation is in exact opposition to the theory of substitution of M. Dumas. 



On some New Oxides of certain of the Metals of the Magnesian Family. 

 By Dr. Lyon Playfair. 



The author first drew attention to the defective state of our knowledge regarding 

 the oxides of the magnesian family. Iron and manganese possess sesquioxides, but 

 copper and zinc do not. Manganese has a high degree of oxidation represented by 

 the formula R 3 , but none of the other metals mentioned have an analogous oxide. 

 There is nothing in the molecular structure of the metals to account for this dif- 

 ference. It is indeed true that Thenard has described compounds of copper, zinc, 

 and calcium, to which he has ascribed the general formula of peroxide of manga- 

 nese. But these compounds do not possess any chemical characters in common 

 with that oxide. They are very unstable bodies, being decomposed spontaneously in 

 air, and more rapidly so by heat, by alkalies, and by acids ; they are formed by the 

 action of peroxide of hydrogen on .the protoxides of the metals. The author had 



d2 



