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IKTRODUCTION
Previous investigations 1-4 have shown that the thcrmobalancc could be usccl for the determination of "hygroscopic moisture", organic matter ancl inorganic carbot~ntcs in soils. During the course of this work weight losses at high tcmperaturcs (> 1000~) indicated that thermogravimetry might be cxtencled to the analysis of chlorides and sulphates in soils if furnace temperatures could be rnisccl by several hundrccl clegrccs. This was also suggested by the work of GUENNELON~.
In orclcr to meet these conditions the Stanton Recording Thermobnlance was modified by the installation of a platinumwound high temperature furnace, which permitted heating under controlled conclitions up to 1335~.
The investigation was limited to those chlorides and sulphates which arc known to occur in soils in larger than%race amounts, i.e. the chlorides and sulphates of potassium, sodium, calcium and magnesium.
Since very limited information on the pyrolysis of these substances was found in the literature it was first necessary to study the thermogravimetry of the pure salts. The information thus obtained was applied to the analysis of saline soils.
ESPERIMENTAL
A&hmztrrs
A Stanton Recording Thermobalance of 0.x mg sensitivity modified by the installation of a T1400 high temperature furnace was used and the samples wcrc held in platinum crucibles. The rate of heating was approximately 400' per h. The data as recorded by the thermobalance were replotted as loss of weight (Y axis) vs. tcmperature' (S asis). Prolonged heating at constant temperature was indicated by hatch marks on the curves.
Materials
Soils known to contain chlorides and sulphates were obtained from the Salinity Laboratory, Riverside, California, U.S.4. and from the Soil Substation, Vegreville, Alberta, Canada, respectively. Finely-ground air-dried soil samples were used throughout. All chemicals used were of the highest purity available commercially.
l Contribution so. 37, Soil Research Institute and No. II.
Service. Analytical Chemistry Rcscarch
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