394 
The procedure inyolves the use of brilliant 
two-colored indicators, such as those recom- 
mended by Clark and Lubs, applied to soil 
extracts obtained without filtration by the use 
of a centrifuge. 
In work being published elsewhere, L. A. 
Hurst and the writer have compared the elec- 
trometric method with the improved colori- 
metric method as described by Clark and 
Lubs? and have found a very close agreement 
in the results of the two methods applied to 
soils. We have found it advisable for soil work 
to use the phenol-sulfon-phthalein indicaters 
in water solution as the monosodium salts, and 
to use (pure) methyl red, without neutraliza- 
tion, in alcoholic solution. 
In previous papers from this laboratory the 
suggestion has been made that the occurrence 
of the common potato scab may be limited by 
the hydrogen-ion concentration of the soil.t 
In the work mentioned above this seems to 
have been demonstrated. 
There haye been located now two points of 
interest on the scale of hydrogen-ion exponents - 
for soils: (about) 6.0, the acid limit for 
Azotobacter, and (about) 5.2, the acid limit 
for the potato-scab organism. In addition to 
these organisms, other important soil organ- 
isms have been studied in their relation to 
hydrogen-ion exponent in culture media. In 
general, such pure culture studies should be 
supplemented with soil studies, for a number 
of reasons, one of which is that strains of 
unusual resistance to acidity might be missed 
in the study of a limited number of strains 
in pure culture. 
From the considerable quantity of work 
done some years ago in culture media, it was 
to be expected that limits of hydrogen-ion 
concentration should be discoverable for the 
growth and survival of microorganisms in soil, 
providing only that the soil has a definite and 
significant hydrogen-ion concentration. That 
the soil has definite and biologically significant 
3 Jour. Bact., Vol. 2, Nos. 1, 2, 3, 1917. 
4Gillespie and Hurst, Soil Science, Vol. 4, pp. 
313-319, 1917, and Gillespie, Phytopathology, Vol. 
8, pp. 257-269, 1918. 
5H. g., E. B. Fred, Abstracts of Bacteriology, 
Vol. 2, pp. 10-11, 1918. 
SCIENCE 
[N. 8. Von. XLVIII. No, 1242 
hydrogen-ion concentration has been demon- 
strated by the work of this laboratory. The 
expectation may be different with regard to 
the growth of crops, since (1) very little work 
involving real control of hydrogen-ion con- 
centration has been done on this subject,® and 
(2) the welfare of crops may depend in some 
cases on the success of Azotobacter, of lezume 
bacteria, or of other microorganisms less re- 
sistant to acidity than the plant itself. We 
do not yet know whether, for instance, a point 
can be located, in acid soils not altogether 
infertile, beyond which acidity the growth of 
red clover is always more or less unsatisfac- 
tory; we have seen, however, some indications 
that such a point may exist at about the ex- 
ponent 5. . 
L. J. Gm.esPir 
BuREAU OF PLANT INDUSTRY, 
WasHINeTON, D. C. 
THE NEED OF ANOTHER PHILANTHROPIST BY 
ORGANIC CHEMISTS 
WAntTED, available sets of the greatest of all 
reference books in organic chemistry, Beil- 
stein’s “ Handbuch der Organischen Chemie,” 
for the immediate use of organie chemists in 
the numerous governmental and industrial 
laboratories. Why? Because these chemists 
have been laboring under a serious handicap 
for the past four years, especially in the prep- 
aration of war chemicals and explosives, medic- 
inals, and dyestuffs. How can this pressing 
need be met? In a timely editorial in the 
September number of The Journal of Indus- 
trial and Engineering Chemistry Dr. Charles 
H. Herty has shown that photographic meth- 
ods are available for the reproduction of this 
valuable work at a comparatively low cost. 
Who is to finance the preparation of the zine 
etchings? There is probably some man of 
wealth who can appreciate the present need of 
the organic chemist and come to the rescue. 
The need is urgent. It should be met and 
met immediately. 
The first appealt for financial assistance in 
6See Hoagland, Sotl Science, Vol. 3, pp. 547- 
560, 1917, who studied the barley plant. 
1 Screnoz, N. §., Vol. XLVII., pp. 225-228 and 
pp. 590-591. 
