320 report — 1879. 



A similar experiment, was made with benzene in order to compare quantitatively 

 illuminative value of the two hydrocarbons : — 



the 



The weight of benzene required to maintain the light of 16 standard candles 

 for one hour is 16-5 grams. The mixture consisted of 4*83 cubic feet of hydrogen 

 and 0-17 cubic foot of benzene. Thus, while hydrogen must be mixed with ^th 

 its volume of pentane to yield a gas of the illuminative value of ordinary coal gas, 

 it requires only about ^th its volume of benzene. The illuminative value of 

 benzene is 2'46 times greater than that of pentane, comparing the two by weight, 

 and 2-66 times greater comparing equal gaseous volumes of the two. 



If the light of a hydrocarbon flame is due to the incandescence of the carbon, 

 or highly condensed hydrocarbons, formed at the temperature of combustion, it 

 would seem that the products or mode of decomposition of the two hydrocarbons 

 must differ. If the carbon of each were separated, their illuminative value would 

 be similar. Actually carbon present as benzene vapour has 2-05 times the illumi- 

 native of carbon present as pentane. 



10. The New Condenser. By George S. Hazlehurst, 



I have striven to make my condenser a contrast in every possible way to the 

 usual method. Its principle is the exact opposite of condensing towers. Cold by 

 rarefaction is the old idea — the gas, attenuated by the chimney draught, is drawn 

 through long lengths of expensive glass tubing, through towers of Yorkshire flag, 

 5 feet square and 50 or 60 feet in height, thence to a brick tower, where it is 

 drenched with water, thence to the chimney — sometimes not quite innocuous 

 even then ! 



The new idea is cold by compression. Not new to science by any means, but 

 new as far as muriatic acid is concerned. The difficulty has been to find a valve 

 which would not be eaten up by even an hour's work in the hot and powerful gas 

 — no valve would stand it — but if by any conceivable means the wear and tear and 

 motion of the valve could be thrown solely upon the acid liquor itself, the difficulty 

 would be overcome. 



This single ray of hope soon broadened into fuller light. It was evident if a 

 long pipe were placed, say 3 inches deep, in liquor in a closed vessel, it woidd be 

 much easier to draw air down the pipe and make it bubble through the liquor than 

 it would be to press the liquor up the tube to any considerable height ; make it 

 easier for the gas to enter than to get back ; provide a readier outlet trapped in 

 similar fashion, and you have at once a suction and a delivery. 



Four large ebonite tubes, 30 inches diameter, closed at the upper end, rising 

 and falling in liquor, alternately pull in the gas through one set of liquor traps and 

 expel it through a second, making sufficient draught to take the gas from a pot and 

 furnace whose farthest door is fifty yards distant. The suction valve is so arranged 

 that when full it overflows into the delivery valve, and this again overflows into a 

 cistern. Thus the valves are made to regulate themselves, they merely require a 

 small supply of liquor, and apply themselves naturally to their work. In first cost, 

 in wear and tear, and in the amount of water used, the patent offers larger 

 advantages compared with condensing towers. 



It soon became evident that the enormous amount of heat evolved from pot 

 and furnace, and also from the gas itself by the very act of condensation, would 

 prove a serious drawback. Fifteen-inch vertical pipes, chequered with tiles, and 

 supplied with a stream of cool strong acid or water have hitherto sufficiently 

 reduced the temperature to make it safe to use the ebonite tubes. The greatest 



