Jan. 26, 1924 
Changes in Hydrogen-Ion Concentration 
2 11 
ungerminated seeds changed the initial reaction of single salt solutions. 
As it was the intention to limit this study to the changes produced by 
the metabolic processes of growing seedlings, however, this procedure, 
by which the prevention of contact between seeds and the experimental 
solutions was assured, seemed best. This procedure also made it pos¬ 
sible to grow more seedlings in a single culture than the cork method 
generally used in studies of this nature. 
CHANGES OF REACTION IN SOLUTIONS OF VARIOUS ACIDS 
The salts of the inorganic acids selected for this experiment are com¬ 
monly found in soils and are used as fertilizers. The elements which 
enter into their composition have various functions in plant life and are 
present in different quantities in plant substance. Their quantitative 
order is: Nitrogen, phosphorus, sulphur, and chlorin. Functionally, 
chlorin is considered the least important. A certain number of organic 
acids were used for the sake of comparison. The experiment was run in 
duplicate. Samples for analysis were pipetted out through a hole made 
in the paraffined paper cover. The P H values were determined colori- 
metrically. The checks usually were very good. The figures in the 
tables represent in the majority of cases averages of two determinations. 
Five seedlings per culture were used in this experiment. The initial 
reactions of the acid solutions were P H 4 and P H 3. 
Of the inorganic acids with an initial P H value of 4, nitric acid 
decreased most in acidity (Table II). The differences involved were 
small but consistent, and reappeared when the solutions were renewed. 
The value of P H 5, obtained twice in the nitric acid solution, indicates 
that practically all the acidity attained by the addition of the acid was 
eliminated, as the untreated distilled water used had an acidity of about 
P H 5.3, owing to the presence of carbon dioxide. The results with the 
inorganic acids of the initial P H 3 series are inconclusive, owing to the 
small size of the changes produced, which makes the observations more 
subject to experimental error. 
Tabi,F II .—Changes of reaction produced by growing wheat seedlings in solutions of 
acids 
Acid. 
| Reaction of solution having an initial Ph of 4. 
Reaction of 
solution 
having an 
initial Ph 
of 3 after 
9 days. 
j After 
j 1 day. 
i_J_ 
After 
2 days. 
After 
3 days. 
After 
10 days. 
Hydrochloric. 
P H' 
! 4 - 5 ° 
P H' 
4. 70 
P H- 
<*4.65 
64. so 
P B' 
3-0 
Nitric. 
! 4 - 70 
5. OO 
a 4. 90 
&S-00 
3 * 1 
Sulphuric.! 
4- 65 
4. 70 
a 4 - 70 
? 4 - 75 
3 -1 
Phosphoric. 
4. 60 
4. 80 
a 4. 80 
6 4- 70 
3 -1 
Formic. 
4- 65 
a 6. 10 
a » c 6. 10 
6. 40 
6.4 
Acetic. 
4. 20 
4 - 50 
5 - 5 $ 
6. go 
3 - 1 
Oxalic.j 
4. 80 
a 6 . 10 
a » c 6. 10 
ft 6. 40 
6.4 
Succinic. 
4. 00 
4.40 
4.90 
6. 40 
3 -o 
Benzoic.! 
4. 00 
4. 20 
4.95 
6. 45 
3 * 0 
Phthalic.:. i 
1 
1 
4. 00 
4. 00 
4. 60 
4 * 5 ° 
3 -o 
a Solution renewed after this reading was obtained. b Seven-day contact. c One-day contact. 
