At the twenty-fourth annual meeting of the Gas Institute, which was recently held in Glasgow, Dr. Stevenson Macadam, F.R.S.E., lecturer on chemistry, Edinburgh, submitted the first paper, which was on "Gas from Oil."
He said that during the last seventeen years he had devoted much attention to the photogenic or illuminating values of different qualities of paraffin oils in various lamps, and to the production of permanent illuminating gas from such oils. The earlier experiments were directed to the employment of paraffin oils as oils, and the results proved the great superiority of the paraffin oils as illuminating agents over vegetable and animal oils, alike for lighthouse and ordinary house service.
The later trials were mainly concerned with the breaking up of the paraffin oils into permanent illuminating gas. Experiments were made at low heats, medium heats, and high heats, which proved that, according to the respective qualities of the paraffin oils employed in the trials, there was more or less tendency at the lower heats to distill oil instead of permanent gas, while at the high heats there was a liability to decarbonize the oil and gas, and to obtain a thin gas of comparatively small illuminating power. When, however, a good cherry red heat was maintained, the oils split up in large proportion into permanent gas of high illuminating quality, accompanied by little tarry matter, and with only a slight amount of separated carbon or deposited soot.
The best mode of splitting up the paraffin oils, and the special arrangements of the retort or distilling apparatus, also formed, he said, an extensive inquiry by itself. In one set of trials the oil was distilled into gaseous vapor, and then passed through the retort. In another set of experiments, the oil was run into or allowed to trickle into the retorts, while both modes of introducing the oil were tried in retorts charged with red hot coke and in retorts free from coke.
Ultimately, it was found that the best results were obtained by the more simple arrangement of employing iron retorts at a good cherry red heat, and running in the oil as a thin stream direct into the retort, so that it quickly impinged upon the red hot metal, and without the intervention of any coke or other matter in the retorts. The paraffin oils employed in the investigations were principally: (1) Crude paraffin oil, being the oil obtained direct from the destructive distillation of shale in retorts; (2) green paraffin oil, which is yielded by distilling or re-running the crude paraffin oil, and removing the lighter or more inflammable portion by fractional distillation; and (3) blue paraffin oil, which is obtained by rectifying the twice run oil with sulphuric acid and soda, and distilling off the paraffin spirit, burning oil, and intermediate oil, and freezing out the solid paraffin as paraffin scale. The best practical trials were obtained in Pintsch's apparatus and in Keith's apparatus.
After describing both of these, Dr. Macadam went on to give in great detail the results obtained in splitting up blue paraffin oil into gas in each apparatus. He then said that these experimental results demonstrated that Pintsch's apparatus yielded from the gallon of oil in one case 90.70 cubic feet of gas of 62.50 candle power, and in the second case 103.36 cubic feet of 59.15 candle gas, or an average of 97.03 cubic feet of 60.82 candle power gas.
In both cases, the firing of the retorts was moderate, though in the second trial greater care was taken to secure uniformity of heat, and the oil was run in more slowly, so that there was more thorough splitting up of the oil into permanent gas. The gas obtained in the two trials was of high quality, owing to its containing a large percentage of heavy hydrocarbons, of which there were, respectively, 39.25 and 37.15 per cent., or an average of 38.2 per cent., while the sulphureted hydrogen was nothing, and the carbonic acid a mere trace. Besides testing the gas on the occasion of the actual trials, he had also examined samples of the gas which he had taken from various cylinders in which the gas had been stored for several months under a pressure of ten atmospheres, and in all cases the gas was found to be practically equal to the quantity mentioned, and hence of a permanent character.
By using Keith's apparatus the results obtained were generally the same, with the exception that an average of 0.27 per cent. of carbonic acid gas and decided proportions of sulphureted hydrogen were found to be present in the gas. Dr. Macadam devoted some remarks to the consideration of the question as to how far the gas obtained from the paraffin oil represented the light power of the oil itself, and then he proceeded to say that, taking the crude paraffin oil at 2d. a gallon, and with a specific gravity of 850 (water = 1,000), or 8½ lb. to the gallon, there were 264 gallons to the ton, at a cost of £2 4s. per ton. The sperm light from the ton of oil as gas being 3,443 lb., he reckoned that fully 6 lb. of sperm light were obtained from a pennyworth of the crude oil as gas.
Then, taking the blue paraffin oil at 4d. per gallon, and there being 255 gallons to the ton, it was found that the cost of one ton was £4 5s., and as the sperm light of a ton of that oil as gas was 5,150 lb., it was calculated that 5 lb. of sperm light were yielded in the gas from a pennyworth of the blue oil. The very rich character of the oil gas rendered it unsuitable for consumption at ordinary gas jets, though it burned readily and satisfactorily at small burners not larger than No. 1 jets.
In practical use it would be advisable to reduce the quality by admixture with thin and feeble gas, or to employ the oil gas simply for enriching inferior gases derived from the more common coals. On the question of dilution, he said that he preferred to use carbonic oxide and hydrogen, and most of the remainder of his paper was devoted to an explanation of the best mode of preparing those gases (water gases).
He concluded by saying: The employment of paraffin oil for gas making has advantages in its favor, in the readiness of charging the retorts, as the oil can be run in continuously for days at a time, and may be discontinued and commenced again without opening, clearing out residual products, recharging and reclosing the retorts. There is necessarily, therefore, less labor and cost in working, and as the gas is cleaner or freer from impurities, purifying plant and material will be correspondingly less. Oil gas is now employed for lighthouse service in the illumination of the lanterns on Ailsa Craig and as motive power in the gas engines connected with the fog horns at Langness and Ailsa Craig lighthouse stations. It is also used largely in the lighting of railway carriages. Various populous places are now introducing oil gas for house service, and he felt sure that the system is one which ought to commend itself for its future development to the careful consideration and practical skill of the members of the Gas Institute.