MECHANICS AND USEFUL ARTS. 85 



and labor, by its use instead of coal. As the bitumen also yields 

 double the quantity of gas, there is a saving of one half in the labor 

 of handling the material. The chief part of all the gas consumed in 

 Great Britain and the United States is obtained from common bitumi- 

 nous coal, the average product of six varieties of which is 2.70 cubic 

 feet from the pound, with a specific gravity of 0.529. The illuminat- 

 ing power of these gases is proportional to their specific gravity. Bi- 

 tumen of the poorest quality gives five cubic feet to the pound , with a 

 specific gravity of 0.720 Therefore the illuminating power of the 

 gas from a pound of bitumen is to that obtained from a pound of coal 

 (Liverpool) as 6.25 to 2.70. The cost of the material (coal) that 

 now supplies gas for New York must be estimated at $ 1 for every 

 1,000 cubic feet of gas. The bitumen may bs abundantly supplied for 

 $5 per ton. The cost of bitumen, therefore, to supply 1,000 cubic 

 feet of gas, would be only $ 0.38. At a moderate calculation, by sub- 

 stituting bitumen for coal, the gas may be supplied to the consumer at 

 less than one half of its present cost, and the manufacturer still make 

 a profit. 



The inquiry at once presents itself, what are the resources of bitu- 

 men or asphaltum? In reply, it may be stated that the lake of bitu- 

 men of Trinidad is altogether inexhaustible, and might furnish sup- 

 plies for the whole world. Besides the abundance of this mineral 

 along the whole coast of South America, Mexico, and Texas, it 

 abounds in the island of Cuba, where a single stratum, six miles from 

 Havana, is no less than 144 feet in perpendicular thickness. Thus 

 far the employment of this substance, so astonishingly abundant, has 

 not even been engaged in or undertaken for a practical purpose. 

 Scientific American, Feb. 16. 



PURIFICATION OF COAL-GAS. 



AT the meeting of the Society of Arts, on April 24, Mr. Laming 

 read a paper on the above subject. After some preliminary observa- 

 tions, the author described his new process, \vhich has been success- 

 fully tried at the Westminster Works with 7,000 cubic feet of gas per 

 hour, and is now being used with purifiers ten feet square. The puri- 

 fying material, through which the impure gas is first passed, with- 

 draws from it 17 parts of ammonia, 17 sulphuretted hydrogen, and 22 

 carbonic acid. It consists of a saturated solution of muriate of iron, 

 decomposed by chalk or lime into muriate of lime and hydrated pro- 

 toxide or carbonate of iron, and then mixed with breeze or sawdust, to 

 absorb it. During the mixing the iron becomes highly peroxidized 

 by the atmosphere. After a time the purifying material seems to be 

 exhausted and ceases to act ; but if we pass through it a current of at- 

 mospheric air, it becomes revivified and acts as well as before. This 

 process of revivification takes but an hour or two, and it has been re- 

 peated fifteen times ; but a period will arrive when the material must 

 be well washed to get rid of the ammoniacal salts formed, when it will 

 be restored to its pristine condition. The advantages obtained by this 

 process are, that the gas is completely purified with an increase in 



8 



