Nov. II, 1918 Soil Acidity as Affected by Moisture Conditions 



323 



Table II. — Relative acidities of soils with different moisture conditions, and changes 



due to drying 



Soil. 



A«... 



B.. 



Moisture treatment 



Potassium-nitrate 

 method." 



Moist. Dried. Change 



3>950 

 Si 67s 

 8,000 



S»46o 

 4, 160 

 6, 150 

 3.475 



2, 220 

 I, 720 

 3, 100 

 3.725 

 1.775 



460 

 360 

 650 

 975 

 450 



2,520 

 2,360 

 3.12s 

 3.62s 

 1,850 



5. 080 

 5,000 

 4,000 

 5.400 

 6, 720 



+ 25 

 + 100 

 — 42s 



— 75 



— 25 



— 1,700 



+ 250 

 + 325 

 -1.850 



+ so 



— 275 



— 1,280 



Calcium-acetate method.' 



Moist. Dried. Change 



9.500 



7,000 



6,250 

 7.500 

 6, 500 



8,000 

 8,750 

 6,250 



10,750 

 II, 500 

 12,000 



63,500 

 72,500 

 76,000 



5,875 

 7, 000 

 9.000 

 6,250 



4.875 

 5, 000 

 6, 250 

 7,000 

 5,500 



8,12s 

 7,500 

 9,000 

 10,000 

 5.000 



10,625 

 9,500 

 13,000 

 12, 500 

 9,500 



69. 7SO 

 66,000 

 63.500 

 65,000 

 69,500 



— 500 



— 750 



- 500 

 -1,000 



-1-1,000 

 -1-1,250 

 — 1, 250 



+ 2, 250 

 -|-i,ooo 

 —2,500 



-7.500 

 -6,500 



Ethyl-acetate method.'' 



Moist. Dried. Change. 



0.0011 

 .0009 



• 0034 

 .0038 

 . 0026 



. 0027 

 . 0029 

 ■ 0025 



.0081 

 . 0090 

 .0090 



.0081 

 .0103 

 .0120 



o. 0006 

 .0006 



.0011 

 . 0017 

 • 0013 



• 0013 



• 0013 



. OOII 



.0050 

 .0050 



• 0055 



.0064 

 . 0064 

 .0060 



-0.0005 

 - .0003 



. 0023 

 ■ 0021 



• 0013 



.0014 

 .0016 

 ■ 0014 



• 0031 

 .0040 



■ 003s 



. 0017 



• 0039 



.0060 



» Results expressed in pounds of calcium carbonate required for 2,000,000 pounds soil. 



t> Ten gm. of soil were placed in 100 cc. of pure 5 per cent ethyl-acetate solution and shaken at frequent 

 intervals. The solutions were kept in a thermostat at 27° C. for 24 hours. Then 10 cc. of the supernatant 

 liquid was removed and titrated with NI20 sodiimi hydroxid, phenolphthalein being used as the indicator. 

 The figures reported are the constants calculated from the formula K^ijt (log aja-x), where a equals grams 

 of ethyl acetate at start and a-x equals grams of ethyl acetate left at t (one day). The constant for Njifioo 

 acetic acid carried under like conditions was o. 0004 and for Nil, 000 nitric acid it was 0.0039. These con- 

 stants are relative only. Autocatalysis was noted in longer time reactions, but this factor has been ignored 

 in the calculations reported. 



c There was not enough of soil A, and the one-fourth water-holding capacity f)Ot was omitted. 



When the samples of moist soil taken at the close of the experiment were 

 air-dried, those samples that had been kept saturated decreased markedly 

 in acidity according to all methods used. When the samples kept at one- 

 fourth and one-half water capacities were air-dried, all deceased in acidity 

 according to the ethyl-acetate method, but the Hopkins and Jones 

 methods gave both increases and decreases in acidity. While the acidity 

 was generally decreased when the soils were air-dried, the degree of acidity 

 equilibrium reached varied to a large extent, owing to the condition of 

 equilibrium caused by the variation in moisture content at which the soil 

 had been held. For instance, while undried soils containing much 

 organic matter gave a higher acidity at full water than at half water 

 capacity, these same soils when air-dried gave a much lower acidity after 

 being held at full water than when held at one-half water-holding 

 capacities. This reversal in order of acidity is not so apparent with soils 

 low in organic matter. 



Preliminary tests were made on the soils from samples taken nine 

 months from the beginning. The results obtained with the samples 

 from the pots of fully saturated soil show the extreme sensitiveness of 



