CHEMISTRY. 



101 



Elements 



of 

 Chemistry. 



Dr Henry's numbers are the result of experiment : 

 Mr Dalton's of experiment modified a little by a happy 

 generalization. He conceives that the degree of the ab- 

 sorption of each of the four sets into which the gases are 

 divided by the horizontal lines in the preceding table 

 may be represented as follows : 



First set, Water absorbs its own bulk = yj 



Second set,- 

 Third set, 

 Foui th set, 



ith its bulk = |T 



_ i_ 

 - 3i 



IT 



TF3 



From this generalization, which holds at least very 

 nearly, it follows that the density of the gases, after ab- 

 sorption, is either the same as before it, or at least some 

 submultiple of it, and the distance between iheir particles 

 is either the same as before, or twice, thrice, or four times 

 as great. 



Dr Henry has shown, that whatever be the density of 

 the gas, the bulk of it absorbed is always the same. If 

 carbonic acid gas be reduced by pressure to twice the 

 usual density, water stillcontinues to absorb its own bulk 

 of it. Hence by increasing the pressure, water may be 

 made to absorb any quantity of a gas whatever. 



The gases still retain their elasticity after they have 

 been absorbed by water, accordingly they make their 

 escape if the water be placed under the exhausted receiver 

 of an air pump. 



The proportion of a gas absorbed by water, depends 

 very much upon its purity. This water absorbs its own 

 bulk of pure carbonic acid gas ; but if the carbonic acid 

 gas be mixed with common air, the proportion of it ab- 

 sorbed is much diminished. Water impregnated with a gas 

 must be in contact with a portion of the very gas absorb- 

 ed, otherwise that gas soon makes its escape altogether. 



As the temperature increases, the absorbability of the 

 gases by water diminishes, no doubt in consequence of 

 the increased elasticity of the gases. 



This absorption of the gases by water is probably the 

 consequence of an affinity between them and that liquid. 

 Hence the determinate proportion of each absorbed, and 

 most of the other phenomena, admit of an easy explana- 

 tion. 



The alkaline and acid gases are very absorbable by 

 water, and of course are acted on by a strong affinity. 

 The following Table exhibits a view of the bulk of each 

 gas absorbed by one measure of water. 



Sulphurous acid, . . S3 

 Fluoric acid, .... 175 -f- 

 Muriatic acid, .... 516 

 Ammoniacal gas. . . 780 



Elemenu 



of 

 Chemistry. 



When a cubic inch of water is saturated with these 

 gases, its bulk increases. The following Table exhibits 

 the bulk of water when thus saturated, supposing the 

 original bulk to have been 1 . 



Saturated with 



Sulphurous acid, 1.040 



Muriatic acid, . . 1.500 



Ammoniacal, . . 1.666 



Thus the water undergoes an expansion, so that the 

 density of the gases absorbed is not in reality so great as 

 it appears to be. The following Table exhibits the real 

 densities of these gases in the water. 



Sulphurous, 

 Muriatic, . 

 Ammonia, . , 



, 31.7 = 3' nearly. 

 344.0 = 7 s 

 468.0 = 8' 



That these gaseous bodies combine chemically with 

 water, cannot be doubted. 



The simple gases have the property of combining with 

 different solid bodies, and of forming compounds some- 

 times gaseous, sometimes liquid, and sometimes solid. 

 Oxygen combines with two dozes of carbon, forming 

 carbonic acid, and carbonic oxide, both gases ; the first 

 a product of combustion, the second a combustible oxide. 

 It combines with three doses of phosphorus, forming 

 oxide of phosphorus, phosphorous acid, and phosphoric 

 acid, all of which are solid bodies. It unites likewise 

 with three doses of sulphur, and forms oxide of sulphur, 

 sulphurous acid, and sulphuric acid ; the first a solid, the 

 second a gas, the third a liquid. It combines in various 

 proportions with the metals, and all the metallic oxides 

 are solids. 



Hydrogen appears to combine in at least two propor- 

 tions with each of the other simple combustibles. It 

 unites also with several of the metals, but the proportions 

 have not been ascertained. 



CHAP. II. 

 Of Liquids. 



A LIQUID is a fluid, not sensibly elastic, the parts of OfLi<juiJ. 

 which yield to the smallest impression, and move easily 

 upon each other. All liquids have a certain cohesive 

 force by which their particles are retained together, and 

 this force is much greater in mercury than in water. The 

 following Table exhibits a list of liquids, with their rela- 

 tive specific gravities. 



Water 1.000 



Ethers 0.632 to 0.900 



Prussic acid 0.70.5 



Petroleum 0.730 to 0.878 



Volatile oils 0.792 to 1.094 



Alcohol 0.796 



Fixed oils 0.913 to 0.968 



Supersulphureted hydrogen 



Nitric acid 1 .583 



Sulphuric acid 1.885 



Phosphuret of sulphur .... 



Mercury 13.568 



