114 SEWAGE AND ITS PURIFICATION 



ordinary green Penicillium glaucuni, which Hanriot found to 

 contain lipase,^ besides emulsin and other ferments. Moulds 

 are not commonly present in the anaerobic stage, but occur in 

 the second or limited aeration. Ritthausen and Baumann 

 found that a great destruction of fat occurred by the action of 

 moulds and bacteria in a substance containing proteids as well. 

 The substance they experimented on was rape-cake.^ The 

 glycerine also ferments. R. Sazerac discovered a bacterium 

 which has the power of rapidly oxidizing glycerine.^ 



8. The Sulphur Fermentation. — Sims Woodhead found 

 Bacterium sulphureum in the Exeter tank. It liquefies gelatine, 

 casein, and other albuminoids, and produces sulphuretted 

 hydrogen. Several observers did not, however, find HgS in 

 the tank gases. I have found that a mercaptan (methyl hydro- 

 sulphide) and other ethereal compounds are undoubtedly present 

 in small quantities. They are very soluble and easily oxidized. 



The sulphur fermentations seem to have many stages. 

 Zelinski obtained from Black Sea ooze an organism which he 

 named Bacterium hydrosulphureum ponticum : it reduced sul- 

 phates to sulphides, and evolved H^S. He cultivated it in 

 a special medium containing i per cent, ammonium tartrate, 

 one to 2 per cent, glucose, 0'5 to i per cent, sodium thio- 

 sulphate, o'l per cent, potassium phosphate, and a trace of 

 calcium chloride.^ Letts, using this solution, succeeded in 

 cultivating a similar organism from the foreshore mud of 

 Belfast Lough.^ Martinus Beyerinck^ groups in a new genus 

 Aerohacter — bacteria derived from air, buf facultatively anaerobic, 

 which cause fermentations, giving H, COg, and lactic acid, 

 and also form sulphuretted hydrogen from proteids and from 

 sulphur compounds other than sulphates. They are detected 

 by the blackening of white lead diffused in the cultures. They 

 reduce nitrates to nitrites, but the presence of the former 

 prevents fermentation and gas formation. In air they may act 

 as oxidizers, except the aerobacter known as B. coli communis. 

 " The nauseous odours of putrefaction are not due to sulphides. 

 The reduction of sulphates is due to Spirillum desulphuricans.'' 

 Saltet isolated a B. desulphuricans which reduces sulphates to 

 sulphites, but produces no HgS. 



^ See Kastle and Loevenhart, American Chemical Jovrnal, xxiv., No. 6. 



2 Landw. Versuchs. Stat., xlvii., 386, 1896. 



3 Bull. Soc. Chim. de Paris, [3], xxix., No. 16, 1903. 



* Proceedings of the Russian Physical and Chemical Society, xxv., [5], 1893. 

 5 Proceedings of the Royal Society of Edinbicrgh, March 4, 1901. 

 ^ Arch. Nederland Sci. nat., 1900, [2], iv., i. 



