216 



SCIENCE 



[N. S. Vol. LIII. No. 1366 



salt becomes microscopic in one place; while 

 phosphorus at least tliree times shows its 

 affinity for o by taking up this letter into its 

 last syllable; but all of these are changes 

 which occur frequently in the composing 

 room, and are of minor importance. The re- 

 Tiewer would prefer the Latin to the hybrid 

 spelling of sulfur, the name columbium to 

 niobium throughout, and diatomaceous to in- 

 fusorial earth (since there are no infusoria in 

 it). He also does not believe that classifica- 

 tion of minerals by their metals is less sci- 

 entific than by their non-metals; but that 

 ervery one does not agree on such matters is 

 an advantage to science, and not a detriment 

 to this book. 



To sum up: Because of the excellent illus- 

 trations, the up-to-dateness, and the practical 

 nature of the information furnished, there 

 would seem to be room for this " Mineralogy " 

 even in a somewhat crowded field. 



Edgar T. Wherry 



TJ. S. Department op Agriculture 



SPECIAL ARTICLES 



ACID PRODUCTION BY A NEW SULFUR-OXI- 

 DIZING BACTERIUM 



In a series of investigations on the oxida- 

 tion of sulfur, which resulted in the isolation 

 of a very strong sulfur-oxidizing bacterium, a 

 striking fact has presented itself, namely, an 

 intense oxidation of sulfur to sulfuric acid 

 and a large accumulation of acids, even in the 

 absence of neutralizing substances. 



The organism is autotrophic, i.e., is able to 

 derive its energy not from the decomposition 

 of organic substances, but from the oxidation 

 of sulfur, although the presence of organic 

 substances is not detrimental to its activities. 

 The carbon, necessary for the building up 

 of its body substances, is derived from carbon 

 dioxide of the air. In a medium entirely 

 free from any traces of organic materials 

 and carbonates and containing ammonium 

 salts as sources of nitrogen and some inor- 

 ganic minerals, the organism rapidly oxidizes 

 sulfur into sulfuric acid; the latter acts upon 

 neutralizing substances present in the medium 

 (tricalcium-phosphate has been used chiefly) 



transforming them into salts and acid salts; 

 when all the neutralizing substances present 

 ^ave been used up, free acids begin to accu- 

 mulate. 



Free acidity was measured both by titra- 

 tion, using phenolphthalein as an indicator, 

 and by the determination of the concentration 

 of hydrogen ions, using the phonolsulfoneph- 

 thalein series of indicators added to buffer so- 

 lutions. For the determination of the highly 

 acid solutions, tropaeolin 00, methyl-violet and 

 mauvein were used and the results checked up 

 by the electrometric method. 



The following table is typical of the acid 

 accumulation by the organism : 



TABLE I 



Titration. Co. ot N/10 

 Alkali Required to 

 Neutralize 1 C.c. 

 Age of Culture Ph o( Culture 



At start 5.6 0.16 



33 days 2.2 1.25 



61 days 1.8 2.25 



85 days 0.58 4.00 



The titration does not give a true indication 

 of the true acidity of the meditim, and, al- 

 though the culture, when 83 days old, was 

 equivalent to 0.4 N" acid by titration, the pres- 

 ence of large amounts of soluble phosphates in 

 the medium would tend to diminish the actual 

 free acids in the medium. But the Ph value 

 gives a true indication of the acid concentra- 

 tion of the medium. The highest concentra- 

 tion of acid ever reported for a living phe- 

 nomenon was the production of citric acid by 

 Aspergillus niger, which reaches a Ph equiva- 

 lent to 2.0-1.8 (Clark and Lubsi). The acidity 

 produced by this sulfur-oxidizing organism, as 

 expressed in terms of Ph — 0.58 — is greater than 

 that of any acidity ever reported for biologic 

 phenomena. 



A detailed study on the sulfur oxidation by 

 this organism will soon be published in Soil 

 Science. 



Selman a. Waksman, 

 Jacob S. Joffe 



N. J. Agricultural Experiment Station 



1 W. M. Clark and H. A. Lubs, /. Bad., 2, 1917, 

 1-34, 109-136, 191-236. 



