1845.] 



THE CIVIL ENGINEER AND ARCHITECTS ^JOURNAL: 



ITS 



of the gas, as it escaped from tlie retorts ; he suggested a gradual re- 

 frigerition of the gas, or the retaining it for a short time, at an inter- 

 mediate temperature, such as '212'' Fahrenheit, hcfore it was cooled 

 down to the temperature of the air, in the usual refrigerators. Tlio 

 tarry mutters in tlie gas, being the least volatile, would tiius oondensi' 

 first, and by themselvis, at a temperature which, b'ing inadequate to 

 condense the naphtha, would prevent tlii'ir carrying down with them, 

 so much of the valuabli' naphtha vapour, as at present. These tarry 

 matters having an afllnity for naphtha, tended powerfully to denaph- 

 thalize the gas, when in contact with it at a low temperature, and to 

 deprive it of that valuable adjunct for combustion. Professor (iraham 

 had found, that by mixing an equivalent proportion of sulphate of 

 soda with the lime, more than twice the quantity of sulphuretted hy- 

 drogen was taken up. The lime was entirely converted into sulphate 

 of lime or gypsum, and the whole soda became bi-hydro-sulphuret of 

 soda, which might be easily washed out of the former. The latter 

 salt might be again converted into sulphate of soda by roasting it ; 

 aud thus might be used to mix with the lime in the purifiers over and 

 over again. Sulphate of lime, which was tlic only residue, was valu- 

 able for agricultural purposes. — hi the distribution of coal gas, every 

 means for counteracting the porosity of the pipes, should be adopted. 

 In experiments upon cast iron gas-pipes, he had found as much as 25 

 per cent, of atmospheric air, mingled with the coal gas, which had 

 been in the mains for 12 hours. This arose entirely from the porosity 

 of the metal ; air entering by the dillusive power of gases, although 

 the coal gas in the main was under a small pressure. This should be 

 guarded against, not only on account of the positive loss of gas which 

 it indicated, but because, as was well known, a moderate proportion 

 of atmospheric air mixed with the gas, greatly diminished its illumi- 

 niting power. 



Porosity of Iron Pipes. 



Mr. Simpson stated, that in connexion with the subject of gas-mak- 

 ing, \he porosity of the iron pipes, through which it was circulated in 

 the streets, should be noticed. He believed that formerly, consider- 

 able quantities of pipes had been laid without their being previouslv 

 proved ; and even now, experiments he had made convinced him, that 

 few pipes were not in some degree porous. When they were proved 

 with water, under a heavy pressure and a mirror was placed near the 

 surface of the metal, a damp film showed the permeability, and after 

 the pressure had been continued for some time, the exudation of mois- 

 ture was very visible. Oxydation would, to a certain extent, close 

 the pores of the metal and prevent this effect, and he would suggest, 

 that all pipes should be proved with a solution of sal-ammoniac, which 

 being forced into the body of the metal, would effectually oxydize it, 

 and to a great extent cure the evil. He felt convinced, that 25 per 

 cent, of the gas was lost, from the leakage of the pipes and the joints; 

 and in opening the streets, the difference between the gas and the 

 water pipes, was immediately perceived, by the soil around the 

 former being saturated with gas. He quoted an instance where, in a 

 length of 1000 yards of iron pipes 2 inches in diameter, there had 

 been a loss of 357 cubic feet of gas in 24 hours. By perseverance in 

 repairing the escapes, the porous spots and other defects in the metal 

 of the pipes, the leakage had been reduced in three years to about 13 

 cubic feet in 24 hours. 



Mr. Lowe said, that although in the early stages of gas-lighting, the 

 pipes laid in the streets might not have been proved, such was not 

 now the case; at present all were severely tested, and great attention 

 was paid to the formation of /he joints, which wore made by ramming 

 in layers of gasket, previously soaked in hot pitch and tallow, then 

 running in the lead, and aflertliat was well driven up with a caulking- 

 iron, the joint was smeared over with pitch. — The gas companies 

 were fully aware of the loss they had sustained, from defective pipes 

 and bad jointing, and every attention was now given to the subject. 

 Some time since, Mr, Lowe had been called upon, to examine a pro- 

 vincial gas-work, where, although the consumers paid by meter, and 

 an allowance of G cubic feet of gas per hour, was made for each public 

 light, 75 per cent, of the gas which was manufactured, was not ac- 

 counted for. On examination, it was found, that from the ignorance 

 of the superintendent, a pressure of 2 inches of water was kept con- 

 stantly by day upon the pipes. The process of exosmose w'as thus 

 carried on to an enormous extent. As soon as the pressure was dimi- 

 nished, the loss was reduced in proportion, and when, by his advice, 

 the gas was allowed for a time to pass into the pipes, in a less pure 

 state than usual, the leaks were soon discovered and repaired. It was 

 certain, that the process of endosmose and exosmose was constant 

 with gas-pipes, as the cast-iron was of a porous and cellular texture ; 

 and he believed, that a great portion of the loss arose from this per- 

 meability of the metal. He noticud, on opening the streets, aud the 



soil in contact with the whole length of the gas-pipes, was saturated 

 with gaseous products, and not merely those spots near the joints. 



Mr. Fakey observed, that the porosity or permeability of cast-iron 

 was a well-ascertained fact. This first came to his knowledge many 

 y' ars ago, in the case of a hydrostatic or liramah's press, wherein the 

 water, when very forcibly compressed, made its way slowly through 

 the thick cast-iron cylinder by a sort of perspiration at the external 

 surface, so that the press relaxed its pressure and the plunger descend- 

 i-d considerably during the night, after a large package of elastic 

 goods had been left in it, under strong compressure in the evening. 

 The external surface of the cast-iron cylinder was found the next 

 morning, covered with very minute drops of water, particularly to- 

 wards the lower end, where the drops were larger. — As to cast-iron, 

 it was not always a close-grained metal; the carbon, which it con- 

 tained, and which constituted its difference of substance from pure 

 malleable iron, pervaded the mass, divided into minute particles, 

 which kept the molecules of iron apart, and impaired thi'ir cohesion. 

 — Respecting the leakage of gas from cast-iron pipes, a very large 

 proportion proceedeil from the' joints of the lengths of pipes. At 

 Manchester it had been the custom for several years past, to form the 

 joints of cast iron pipes by boring and turning the ends to fit truly one 

 into (he other, aud very recently Mr. Hick, of the firm of Forrester 

 and Co. at Liverpool, had shown him a machine which performed the 

 operation of both boring and turning the two ends of a pipe very ra- 

 pidly. It was a slide lathe bed, having two head stocks with strong 

 mandrils fixed upon it, one near each end ; they were placed at such a 

 distance asunder on the bed, as to receive the length of the pipe be- 

 tween them ; each mandril had a chuck upon the end of it, with 

 notches into which steel cutters were wedged, like a boring head. 

 One such chuck was adapted for boring out the interior of the socket 

 end of the pipe to a suitable cone; the other chuck had its cutters set 

 for turning the exterior, at the other and of the same pipe, to a cor- 

 responding cone. The pipe was fastened down on a sliding carriage, 

 so as to present first one end of it to one chuck, and then the other end 

 of it to the other chuck, by which means the whole operation was very 

 expeditiously and perfectly performed. Thts mode of preparing 

 pipes was becoming common in Liverpool and Manchester, and was, 

 lie thought, deserving of more general adoption. 



Mr. Cooper reminded Mr. Lowe of an experiment at which he was 

 present a few years since, where the process of endosmose and exos- 

 mose was shown very strikingly. A bag formed of two sheets of 

 paper, pasted together all round the edges, was inflated with coal 

 gas, by introducing a quill at the corner ; in 10 seconds it was disco- 

 vered that the gas had entirely escaped and its place was occupied 

 by common atmospheric air, although no visible defect existed in the 

 bag. He thought that the soft and porous quality of the iron of which 

 the pipes were made, for the convenience of drilling and tapping 

 them, for the service branches, conduced to the process and the conse- 

 quent loss of gas. Mr. CroU's system would, he thought, be of much 

 benefit, not only to gas companies, but also to manufactures generally 

 by reducing the cost of ammonia. Some years ago the price of sal 

 ammoniac was 3s. per lb. for a quality inferior to that which was now 

 sold for Hd. per lb. Tiiis reduction was entirely owing to the increase 

 of gas lighting, the products being converted into this useful s;dt. 



In a recent communication from Mr, James Muir, New River 

 Water- works, he observes: — "The coal gas may literally be said to 

 saturate the ground, in localities through which the pipes of several 

 gas companies have been laid ; and it there frequently effects an en- 

 trance into the adjacent water pipes. In seeking a remedy for the 

 evil, the gas companies have been urged to search for their leakages, 

 while the affected service (naturally supposed to be itself defective) 

 has been at the same time stripped,— in some instances driven anew, 

 — and proved, under considerable pressure, to be thoroughly water- 

 tight, but all in vain. This view of the matter induced the proposal 

 of the following simple expedient, as a means of counteracting the 

 evil ; it has in several cases been applied, and in all with full success. 

 From the highest part of the service affected by the gas, a wrought 

 iron tube, 'i inch in diameter, strong enough to resist any tendency to 

 form such a curve as would retain water, is laid evenly, and with an 

 upward inclination, towards the nearest protected situation, such as 

 the side of a house, where it is made to terminate in a vertical piece, 

 extending to any required height above the ground. On the top of 

 this vertical piece is screwed the small float valve fig. 3. The float, 

 A, forms the valve. It consists of a cylindrical piece of cork, in the 

 axis of which a brass wire is fixed, to serve as a spindle for guiding 

 it. The top is covered with leather, by which an air-tight joint is 

 made with the aperture 13 C, above, when the float valve is raised ; 



23* 



