GASSING 625 



is that this diffusion readily takes place in opposition to the law of gravity ; as 

 a light gas, contained in a vessel with an open mouth inverted, gradually descends 

 is diffused into the heavier gas in which it may be placed, and eventually a mixture 

 of the two is effected. 



This subject was very carefully investigated by the late Professor Graham. See 

 his ' Elements of Chemistry,' and Watts's ' Dictionary of Chemistry.' 



GASES, OSMOSE OF. The phenomenon of the passage of a gas through 

 membranaceous diaphragms is so called. See Graham's paper in the ' Philosophical 

 Transactions of the Royal Society.' 



GASES, TRANSPIRATION OP. The passage of gases through capillary 

 tubes. All these phenomena are well explained in Watts's ' Dictionary of Chemistry.' 



GAS-HOLDER. A vessel for containing and preserving gas, of which various 

 forms are described by chemical writers. 



GAS, LAUGHING. Protoxide of Nitrogen ; Nitrous Oxide ; or Nitrogen mon- 

 oxide, NO (N 2 O). This gas is always prepared from the nitrate of ammonia. When 

 this salt is heated in the solid state, it is completely resolved into laughing-gas and 

 water. The heat should be applied with caution so as to avoid too sudden a dis- 

 engagement of gas. Laughing-gas was first described by Priestley in 1776, and 

 carefully studied by Davy. This gas is chiefly remarkable for the peculiar intoxi- 

 cation which it produces when breathed. It is not to be used without much caution. 

 If it is not very pure, serious consequences may ensue ; and even when absolutely 

 pure, the editor has seen the nitrous oxide produce very distressing effects. It has of 

 late been extensively used as an anaesthetic by dentists. 



GASOMETER, means properly a measurer of gas, though it is employed often 

 to denote a recipient of gas of any kind. See GAS, COAL. 



GAS-PIPES. When the illumination by gas was first introduced in the large 

 way by Aaron Manby, Esq., then of the Horsley Iron Works, the old musket-barrels, 

 laid by in quiet retirement from the fatigues of the last war, were employed for the 

 conveyance of gas ; and by a curious coincidence, various iron foundries desisted in 

 a great measure from the manufacture of iron ordnance, and took up the peaceful 

 employment of casting pipes for gas and water. 



The breech-ends of the musket-barrels were broached and tapped, and the muzzles 

 were screwed externally, to connect the two without detached sockets. From the 

 rapid increase of gas illumination, the old gun-barrels soon became scarce, and new 

 tubes, with detached sockets, made by the old barrel-forgers, were first resorted to. 

 This led to a series of valuable contrivances for the manufacture of the wrought-iron 

 tubes, commencing with the Kussell's patent in 1824, under which the tubes were first 

 bent up by hand hammers and swages, to bring the edges near together ; and were 

 then welded between semi-circular swages, fixed respectively in the anvil, and the 

 face of a small tilt hammer worked by machinery, by a series of blows along the tube 

 either with or without a mandrel. The tube was completed on being passed between 

 rollers with half-round grooves, which forced it over a conical or egg-shaped piece at 

 the end of a long bar to perfect the interior surface. 



Various steps of improvements have been since made ; for instance, the skelps were 

 bent at two squeezes, first to the semi-cylindrical, and then to the tubular form pre- 

 paratory to welding, between a swage tool five feet long worked by machinery. The 

 whole process was afterwards carried on by rollers, but abandoned on account of the 

 unequal velocity at which the greatest and least diameters of the rollers travelled. 



In the present method of manufacturing the patent welded tube, the end of the 

 skelp is bent to the circular form, its entire length is raised to the welding heat in 

 an appropriate furnace, and as it leaves the furnace almost at the point of fusion 

 it is dragged by the chain of a draw-bench, after the manner of wire, through a pair 

 of tongs with two bell-mouthed jaws, these are opened at the moment of introducing 

 the end of the skelp, which is welded without the agency of a mandrel. 



By this ingenious arrangement wrought-iron tubes may be made from the diameter 

 of six inches internally, and about one-eighth to three-eighths of an inch thick, to as 

 small as one quarter-inch diameter and one-tenth bore ; and so admirably is the 

 joining effected in those of the best description, that they will withstand the greatest 

 pressures of gas, steam, or water to which they have been subjected, and they admit 

 of being bent both in the heated and cold state, almost with impunity. Sometimes 

 the tubes are made one upon the other when greater thickness is required, but these 

 stout pipes and those larger than three inches are comparatively but little used. 

 (Holtzapffel) 



GASSING. In order to remove the hairy filaments from net-lace and other 

 woven fabrics, they are passed over a large number of minute jets of gas, and between 

 rollers. 



VOL. H. S S 



