FOUL FISH AND FILTH FEVERS. 325 



gas evolves some carbonic and sulphuric acids. Generally, in fairly well-made coal 

 gas, ammonia is absent, but, if present, it occurs only as a slight trace, when it burns 

 off as nitrogen and water. For London the legal maximum is 22 grains of sulphur 

 in winter and 17 grains in summer per 100 cubic feet of coal gas consumed, but the 

 average amount in the metropolis is only 12 grains per 100 cubic feet of coal gas 

 burnt. 



Except perhaps the Siemens hot-blast burners, probably no gas-burner consumes 

 the whole of the coal gas, but always lets some of the gas escape unburnt into the 

 atmosphere. Therefore every room lighted by gas contains, besides carbonic acid, 

 water- vapor, and sulphuric acid derived from the gas, also some carbureted hydrogen 

 and carbonic oxide. Coal gas contains up to 20 per cent of carbonic oxide. Thus 

 Erdmann found in the air of a room which had been lighted by gas 0.056 per thou- 

 sand volumes of carbureted hydrogen (marsh gas). At the same time he discovered 

 that candles burn as a rule still more imperfectly than gas; as much as 0.187 per 

 1,000 volumes of marsh gas resulting in such a case. He also found that candles pro- 

 duce fatty acids and acroleine in the air. 



The following figures by Erdmann may be interesting in this connection. With 

 electric arc light no water-vapor was evolved, and only traces of carbonic acid, and 

 only from 57 to 158 calories of heat. With the Siemens hot-blast burners no carbonic 

 acid or water came into the room. With Argand burners 0.86 kilo water and 0.46 car- 

 bonic acid, with evolution of 4,860 calories. (Siemens burner, 1,500 calories.) With a 

 two-hole burner, 2.14 kilo water and 1.14 kilo carbonic acid, heat 12,150 calories. 



In all gas combustion also some nitrous acid is formed which is very irritating 

 and prejudicial. 



With an incandescent electric-light burner, nothing ought to come into the room 

 and the heat produced is small. 



The worst illuminants as to water and carbonic acid are candles and fluid oils. 



Slaughter-houses, meat stores and shops, fish shops, and fresh-food markets are 

 best illuminated by incandescent electric light, which yields no combustion products. 

 (In the electric arc lights, their carbons burn bodily away, producing carbonic acid.) 



In crowded market-places additional impurities and moisture are given off by 

 the processes of respiration and perspiration, which further contaminate and vitiate 

 a limited supply of repeatedly overbreathed air, especially damp, warm, still air as 

 occurring during fogs, mist, rain, etc. 



During sunlight and activity it appears that an average adult will, through his 

 perspiration and respiration, give off roughly about, more or less, 3 ounces of water 

 per hour, besides considerable organic impurities and some carbonic acid. (During 

 sleep these exhalations are considerably diminished.) 



In densely frequented markets much dirt is unavoidably brought in from the 

 streets, stables, etc., sticking to the boots of the visitors. This wet mud and filth 

 necessarily adhere to the too porous, uneven, damp, dirty pavements of many of our 

 market-places. 



As to the impurities produced by respiration, besides carbonic acid and water, 

 there are always formed ammonia, volatile organic fatty acids, sulphureted hydrogen. 



Seegen and Nowack have also alleged that respired air always contains organic 

 hydrocarbons, but this is doubtful, and any that may be found comes more likely from 

 the intestines. 





