M. Than on Oxysulphide of Carbon. 453 



Than* has described an oxysulphide of cavbon having the for- 

 mula €OS, and which therefore may be regarded as carbonic 

 acid in which an atom of oxygen is replaced by sulphur. It may 

 be prepared in no inconsiderable quantities by passing carbonic 

 oxide with excess of sulphur vapour through a red-hot porcelain 

 tube ; it is, however, mixed with carbonic oxide, from which it 

 could not be separated. The method of preparing the gas in a 

 pure state depends on the following theoretical considerations. 

 Hydrated cyanic acid may be most simply regarded as the imide 

 of carbonic acid, (CO)" H N; and in its decomposition with water 

 carbonic oxide is replaced by two atoms of hydrogen, by which 

 ammonia and carbonic acid are formed, in accordance with the 

 equation 



{GO)" HN + H 2 = H 3 N + GO*. 



If this be the case, hydrosulphocyanic acid should yield by the 

 action of dilute acids ammonia and oxysulphide of carbon, 



(€&)'' HN + H 2 0=H 3 N + £OS. 



Experiment has confirmed this supposition most completely. 

 When powdered sulphocyanide of potassium is added to a cold 

 mixture of sulphuric acid and water, a disengagement of the gas 

 in question ensues, which may be easily controlled by increase or 

 diminution of temperature so as to have a regular current. The 

 gas is passed through a tube containing cotton rubbed with moist 

 oxide of mercury to retain acids (hydrocyanic and probably a 

 trace of formic), through] a tube containing very small pieces of 

 unvulcanized india-rubber to retain bisulphideof carbon (which can 

 be recommended as a most effectual means for the purpose), and, 

 lastly, through a third tube containing chloride of calcium. The 

 purified and dried gas is collected over mercury. If both be quite 

 dry, the gas may be preserved for some days without any change; 

 but if there be any moisture, the surface of the mercury be- 

 comes coated with sulphide in the course of a few hours. 



The gas thus purified has an odour resembling carbonic acid, 

 which at the same time suggests the odour of resin and sulphu- 

 retted hydrogen, but is not unpleasant. Water absorbs about an 

 equal volume of the gas, and acquires its odour ; but immediately 

 afterwards it changes into the peculiar sharp stinging taste, sug- 

 gestive of both sulphuretted hydrogen and sulphurous acid. 



The density of the gas (2*1046) is twice that of air, and it can 

 therefore be poured from one vessel into another. The substance 

 has a feebler acid reaction than carbonic acid. 



It is very inflammable, being immediately inflamed even by a 

 scarcely glimmering spill. It burns with a beautiful blue and 



* Liebig's Annalen, (Suppl.) vol. v. p. 236. 

 Phil. Mag. S. 4. Vol. 35. No. 239. June 1868. 2 II 



