GAS. 



of the process, to a mixture of nitrogen. 

 It may also be expelled from the red 

 ox de of mercury, or that of lead ; and 

 still better from the black oxide of man- 

 ganese, heated red hot in a gun barrel, 

 or exposed to a gemlt-r heat in a retort, 

 with half its weight, or somewhat more, 

 of strong sulphuric acid. To obtain it of 

 the greatest purity, however, the hyper- 

 oxymuriate of potash is preferable to any 

 other substance, rejecting the portions 

 that first come over, as being debused 

 with the atmospheric air in the retort. 

 Growing vegetables, exposed to the solar 

 light, give out oxygen gas ; so do leaves 

 laid on water in similar situations, tKe 

 green matter that forms in water, and 

 some other substances. 



Oxygen gas has neither smell nor taste. 

 It is a little heavier than atmospheric air; 

 under great pressure, uaier may be made 

 to take up about half its bulk. It is essen- 

 tial to the support of life; an animal will 

 live in it a considerable time longer than 

 in atmospheric air ; but its respiration be- 

 comes hurried and laborious before the 

 whole is consumed, and it dies; though 

 a fresh animal of the same kind can still 

 sustain life for a certain time in the resi- 

 duary air. 



Combustion is powerfully supported by 

 oxygen gas ; any inflammable substance, 

 previously kindled, and introduced into 

 it, burns rapidly and vividly. If an iron 

 or copper wire be introduced into a bot- 

 tle of oxygen gas, with a bit of lighted 

 touch-wood or charcoal at the end, it 

 will burn with a bright light, and throw 

 out a number of sparks. The bottom of 

 the bottle should be covered with sand, 

 that these sparks may not crack it. Mr. 

 Accum says a thick piece of iron or 

 steel, as a file, if made very sharp at the 

 point where it is first kindled, will burn 

 in this gas. If the wire, coiled up in a 

 spiral like a corkscrew, as it usually is in 

 this experiment, be moved with a jerk 

 the instant a melted globule is nbout to 

 fall, so as to throw it against the sides of 

 the glass, it will melt its way through in 

 an instant, or if the jerk be less violent, 

 lodge itself in the substance of the glass. 

 If it be performed in a bell-glass set in a 

 plate filled with water, the globules will 

 frequently fuse the vitreous glazing of 

 the plate, and unite with it, so as not to 

 be separable without detaching the glaze, 

 though it has passed through perhaps 

 two inches of water. 



As oxygen gas appears to be a very 



powerful stimulus to the animal econo- 

 my, it has been applied medicinally ; and 

 is reported to have been of great serv-ce 

 in many cases of debility, palsy, nervous 

 affections, scrofula, rickets, and even hy- 

 drocephalus 



GAS, sulphurous acid. When sulphur 

 is burnt slowly, as gas arises, of a suffo- 

 cating pungent smell, consisting of sul- 

 phur combined with oxygen in less pro- 

 portion than is requisite to form sulphuric 

 acid. This was known to the earlier mo- 

 dern chemists, and Stahl examined some 

 of its combinations ; Priestley showed it 

 was permanently elastic ; Berthollet 

 pointed out its difference from the sul- 

 phuric acid ; and Fourcroy and Vauquelin 

 completed its examination. 



In the mode above mentioned, it is very 

 difficult so to regulate the combustion as 

 to obtain it free from sulphuric acid, 

 which is formed when the sulphur burns 

 with a certain degree of rapidity ; so that 

 it is commonly made by subtracting oxy- 

 gen from sulphuric acid by some other 

 inflammable substance. The metals an- 

 swer the purpose, but such as do not de- 

 compose water should be employed, 

 otherwise more or less hydrogen will be 

 evolved. Tin or quicksilver answers best, 

 one part of which may be pnt into a re- 

 tort, with two of concentrated sulphuric 

 acid, and heat applied. It should be re- 

 ceived over mercury, as water absorbs it., 

 taking up thirty-three times its bulk. 



This gas is above twice as heavy as at- 

 mospheric air: it kills animals very 

 speedily,and extinguishes burning bodies. 

 From this latter property it has been re- 

 commended, when a chimney is on fire, 

 to throw a spoonful or two of flowers 

 of sulphur into the grate. It whitens 

 and gives lustre to silk, and is useful 

 in bleaching woollens. Fresh prepared 

 muriate of tin decomposes it, sulphur 

 being deposited, and the muriate oxy- 

 genized. Mr. Northmore has condens- 

 ed it by pressure : and Monge did the 

 same, with the addition of artificial cold. 

 According to Dr. Thompson, it consists 

 of sulphur sixty-eight parts, oxygen thir- 

 ty-two. 



One hundred grains of water take up 

 5 grains of this gas, or 25 parts by mea- 

 sure ; or, according to Dr. Thomson, 8.2 

 grains, equal to 33 times its volume. 

 The solution has a pungent disagreeable 

 odour, and an acid taste, it reddens some 

 of the vegetable colours, such as that of 

 litmus, or red cabbage ; there are others, 



