ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

摘要:

Salinity in soils consists mainly of the chlorides and sulfates of sodium. Estimation of chlorides presents no difficulty. The only method of sulfate estimation heretofore considered reliable, however, has been the gravimetric method, which is time-consuming. It was felt, therefore, that a volumetric method for estimating sulfates would be helpful in the examination of saline soils.

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

摘要:

A practical and reliable method that would indicate quickly under field conditions how much available moisture is in the soil would be of great value, especially since from the standpoint of plant culture such information is more important than a knowledge of the total soil moisture content.Although the method presented here does not indicate directly how much available water is in the soil, it does determine the permanent wilting point of the soil and indicates directly under field conditions whether the moisture is at, above, or below this point.

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

摘要:

All standard methods for determining carbon are so long and complicated as to setup and manipulation that a large number of determinations for total carbon in plant tissues are out of the question. The only colorimetric methods found were one for carbon in steel by the use of nitric acid, which has not proved very satisfactory, and one which measures carbon dioxide from wet combustion.2The latter takes considerable time and necessitates the handling of gases. A great need exists for a direct rapid method for determining carbon in carbohydrate and protein compounds commonly found in plants.When a carbohydrate or protein is heated with sulfuric acid, carbonization takes place, and the depth of color of the liquid is sensibly proportional to the amount of carbon present. Inasmuch as virtually all the carbon of plant tissue, especially vegetative tissue, is in the form of carbohydrate and proteins, and the proportion of carbon compounds that are not charred, such as oxalic acid or stable aromatic compounds, is very small, the color produced by charring with sulfuric acid should be a good index of the amount of carbon in the carbohydrates and proteins present. If it is known that nothing but carbohydrate or protein or substances which are completely charred are present it is an accurate method for determining total carbon.After complete carbonization the solution is diluted with 50 per cent H2SO4and compared to a standard in a colorimeter. The colloidal carbon solutions compare very well and give sharper end points than some colored true solutions.

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1938

数据来源: OVID