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The determination of calcium in phosphate, carbonate, and silicate rocks by flame photometer

Trace Elements Investigations 623

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Abstract

A method has been developed for the determination of calcium in phosphate, carbonate, and silicate rocks using the Beckman flame photometer, with photomultiplier attachement.


The sample is dissolved in hydrofluoric, nitric, and perchloric acids, the hydrofluoric and nitric acids are expelled, a radiation buffer consisting of aluminum, magnesium, iron, sodium, potassium, phosphoric acid, and nitric acid is added, and the solution is atomized in an oxy-hydrogen flame with an instrument setting of 554 mµ. Measurements are made by comparison against calcium standards, prepared in the same manner, in the 0 to 50 ppm range.


The suppression of calcium emission by aluminum and phosphate was overcome by the addition of a large excess of magnesium. This addition almost completely restores the standard curve obtained from a solution of calcium nitrate. Interference was noted when the iron concentration in the aspirated solution (including the iron from the buffer) exceeded 100 ppm iron. Other common rock-forming elements did not interfere.


The results obtained by this procedure are within ± 2 percent of the calcium oxide values obtained by other methods in the range 1 to 95 percent calcium oxide. In the 0 to 1 percent calcium oxide range the method compares favorably with standard methods.

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
The determination of calcium in phosphate, carbonate, and silicate rocks by flame photometer
Series title:
Trace Elements Investigations
Series number:
623
Year Published:
1956
Language:
English
Publisher:
U.S. Geological Survey
Description:
12 p.
Number of Pages:
13