608 REPORT— 1903. 



from which it was drawn by a vacuum pump into two sterilised tubes of sufficient 

 capacity, one of which contained a measured volume of the nitrate solution, and 

 these tubes when filled were closed by pinch-cocks applied to indiarubber junc- 

 tions. At the end of sixty-six hours analyses were made of the dissolved gases 

 contained in the contents of both tubes, when it was found that they were practi- 

 cally identical, and that the nitrate had not been decomposed. The results of this 

 experiment appear to be conclusive. The septic-tank effluent deprived of the 

 micro-organisms which it contains has no action upon a nitrate. The decom- 

 position of the latter must therefore be caused entirely by the vital processes of 

 certain micro-organisms, and not by enzymic or chemical action. 



III. The Micro-organisms which reduce Nitrates with Evolution of Nitrogen 



Gas or Oxides of Nitrogen. 



Gayon, Springer, Deheraine, Maquenne, and others have isolated organisms 

 from putrefying liquids which decompose nitrates with evolution of nitrogen or 

 its oxides, but so far as can be judged from the printed abstracts of their work 

 the identification of the species with known forms was either wanting or was 

 incomplete. It occurred to the authors that as the action is one of reduction it 

 would be worth while to study the effects of those micro-organisms which are 

 known to cause the evolution of hydrogen, such as B. Amylobacter, B. butyricus 

 (Botkin), B. Lactis aerogenes, and B. Coli coynmunis, and as pure cultures of the 

 latter happened to be available experiments were made with them. 



An apparatus was constructed which permitted the introduction of pure cul- 

 tures into a vessel filled with sterilised broth containing potassium nitrate from 

 which the dissolved gases had been removed by boiling out in a vacuum. 



"With this apparatus experiments were first made on the action of pure cultures 

 of B. Coli communis and B. Lactis aerogenes on broth alone. These were con- 

 ducted at ordinary temperatures, and the fluid examined for dissolved gases as soon 

 as a few bubbles of liberated gas had made their appearance. The dissolved gases 

 were found (after removing carbonic anhydride) to consist entirely of hydrogen. 



Experiments were then made with cultures of the same organisms and nitrated 

 broth, and although they are not as yet completed the results so far obtained 

 show that B. Coli communis liberates nitrogen from a nitrate in broth culture ; 

 B. Lactis aerogenes does not do so. 



The authors desire to express their thanks to Professor Lorrain Smith, who 

 supplied the pure cultures and gave most valuable assistance and advice duriug the 

 bacteriological part of the investigation. 



8, On a aiethod fo7' the Separation of Cobalt from Nickel, and the Volumetric 

 Determination of Cobalt. By R. L. Taylor, F.I.C. 



It has been long known that cobalt is precipitated from its solutions as a higher 

 oxide by the carbonates of barium, strontium, and calcium, in presence of chlorine 

 or bromine. Long ago Rose proposed this as a means of separating cobalt from 

 nickel, but he made the mistake of using a strongly acid solution. Of course the 

 excess of acid was neutralised by the added carbonate, but the carbon dioxide 

 thus produced retards enormously, if it does not altogether prevent, the complete 

 precipitation of the cobalt. The author has found ^ that if a perfectly neutral and 

 not too concentrated solution is used, cobalt is precipitated quantitatively as a 

 black oxide in five or ten minutes by either barium or calcium carbonate in pre- 

 sence of bromine water. The two carbonates appear to act equally well, but the 

 former is to be preferred if the subsequent removal of the added metal is desired. 

 Whichever carbonate is used it should be in the precipitated form, and it is best 

 made into a paste with water. If the liquid from which the cobalt is to be pre- 



' Memoirs pf the Manchester Literary and Philosophical Society, \d\.:s\vi. 1^02, 

 No. 11, and vol. xlvii. 1903, No. 12. ■ ' 



