METHODS Or OBTAINING CARBONIC ACID GAS.

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fluid. The. colder the water and the greater the pressure applied,the more carbonic acid gas will be absorbed. The water im-pregnated with it sparkles upon agitation; it has a pungent, aci-dulous taste, and reddens tincture of litmus. Heat again disen-gages the gas from the water. This gas precipitates lime, stron-tia, and barytes, from their solutions in water. It is greedily-attracted by all the alcalies. It undergoes no alteration by light.Its specific weight is to that of atmospheric air as 1500 to 1000.It may be poured out of one vessel into another. It is not actedupon by oxigen, nor is it altered by any of the simple combus-tible bodies at common temperatures ; but phosphorus, iron,and lime are capable of decomposing it, when assisted by heat.

METHODS OF OBTAINING CARBONIC ACID GAS.

Of all the gases, carbonic acid gas is that perhaps, which isdiffused in the greatest abundance throughout nature. It isfound in three different states In that of gas; 2 dly, In

that of mixture ; and 3dly, In that of combination. The vari-ous processes for obtaining it are the following :

1. Put into a common gas-bottle or retort, a little marble,chalk, or lime-stone, and pour on it sulphuric acid, diluted withabout six times its weight of water, an effervescence will ensue,and carbonic acid gas will be liberated, which those who have anopportunity may collect over mercury ; but a mercurial appa-ratus is not absolutely necessary, since the gas may be collectedover water, if it is to be used immediately when procured.

Rationale. ..In this instance the carbonic acid is disengagedfrom the state of combination, and reduced to the aeriform stateof gas. The marble, lime-stone, or chalk consists of this acidand lime ; on presenting to it sulphuric acid, a decomposi-tion takes place, the sulphuric acid has a greater affinity to thelime than the carbonic acid has, it therefore unites to it, andforms sulphate of lime, disengaging at the same time the car-