Gas companies are, as a rule, heavily taxed, and if it were not for a vast amount of idle capital buried in the streets in the form of gas mains, they would probably supply gas at a very low price, especially as the sale of bye-products practically covers the cost of production. Some companies have even reduced the price of gas if used for driving gas engines, and have therefore slightly decreased the cost of production of power by this means.
In France, the home of the oil motor, they are severely handicapped by having to pay double duties on all petroleum entering, first the country itself, afterwards the towns.
Inventors have therefore sought a method of getting round these difficulties by producing a cheap gas, which would answer the same purpose as coal gas. First of all many manufacturers tried to cut down the expense by erecting their own coal gas plants, so as to be independent of arbitrary taxation. The system, although fairly satisfactory, had many drawbacks, and further experiments were made with a view to simplifying the process of production. The result has been to give us water gas and also poor gases, whose great practical value we shall presently demonstrate.
In order to produce what is called water gas, the process essentially consists of placing in contact with one another red-hot carbon and superheated steam. The result is to form a mixture of gases according to the following chemical equation—
3 H2O + 2 C = CO + CO2 + 3 H2.
For those not understanding the above it will be as well to explain, that on the left-hand side of the equation are placed the compounds brought into contact, water (H2O) and carbon (C), and on the right the products of the chemical action, carbon monoxide (CO), carbonic acid gas (CO2), and hydrogen (H2).
The resulting water gas contains 60% of hydrogen and 20% of carbon monoxide, both of which are combustible gases. The proportions of the gases evolved can be varied at will by admitting more steam or using an excess of carbon; by this process a richer gas can be obtained—
C + H2O = CO + H2,
and
5 H2O + 3 C = 2 CO2 + CO + 5 H2.