310 Progress of Invention. 



takes place. He uses chiefly two modes of condensing the vapour ; 

 in one it is transmitted into alcohol, with which it immediately 

 combines, and it is set free as an oily looking liquid, which floats 

 on the surface by the addition of water, glycerine, or anything 

 else for which the alcohol has a stronger affinity than for the ether. 

 The supernatant methylic ether is obtained separate by drawing 

 off the dilute alcohol, which may be rectified for subsequent use ; 

 and it is to be thoroughly dried by the application of fused chloride 

 of calcium, or some other substance having a strong affinity for 

 water. By the second method the ethereal vapour is transmitted 

 into sulphuric acid, which also, if the temperature is kept tolerably 

 low, rapidly dissolves it, forming a solution of methylic ether in 

 sulpbo-methylic acid. Heating this to 120° C, ethereal vapour will 

 pass off, but not at a sufficient pressure to produce condensation. 

 To effect this, which, under the circumstances, requires a pressure 

 of about five atmospheres, the vapour given off by the first solu- 

 tion is transmitted into similarly saturated sulpho-methylic acid, 

 which produces a supersaturated solution ; and when this is dis- 

 tilled, the resulting vapour, which is large in quantity on account of 

 the richness of the solution, is condensed in vessels strong enough 

 to bear the required pressure, 



Decomposition of Sulphurous Acid Gas. — Large quantities of 

 sulphurous acid gas are evolved in certain manufacturing processes : 

 and the escape of these into the atmosphere is not only a waste of 

 valuable materials, but a source of mischief to vegetation, and even 

 to health in the surrounding districts. Many means of preventing, 

 or at least mitigating, this evil have been used ; one of the best has 

 been discovered recently, and is founded on the fact that sulphur- 

 ous acid is decomposed by sulphuretted hydrogen. To decompose 

 the sulphurous acid on the large scale, it is conducted, thoroughly 

 mingled with sulphuretted hydrogen, into a suitable chamber, where 

 the sulphur, in a state of minute division, and fit for many purposes, 

 is deposited ; the results of decomposition being sulphur and watery 

 vapour. The sulphuretted hydrogen is obtained by acting on sul- 

 phuret of barium with dilute hydrochloric acid ; and the chloride of 

 barium which is formed being decomposed with sulphuric acid, the 

 hydrochloric acid is set at liberty, and may be again used for decom- 

 position of sulphuret of barium. 



Simple Mole of Obtaining Chlorine. — The ordinary methods 

 of obtaining chlorine by decomposition of hydrochloric acid are 

 attended with certain inconveniences, from which that invented by 

 M. Parmentier is entirely free. He decomposes the acid by dropping 

 into it small quantities of pulverized chlorate of potash, which im- 

 mediately causes the copious evolution of chlorine, the only residuum 

 being water. This method possesses peculiar advantages when the 

 chlorine is required for the purpose of disinfection ; since it may 

 thus be obtained with great rapidity and ease, and its further evolu- 

 tion may at once be prevented, when enough has been evolved, by 

 the interruption of the supply of chlorate of potash, and still more 

 rapidly by the addition of water to the acid. 



Substitute for the Steam-ham jier. — Nothing has contributed 



