Calcium sulfate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-04-12 to 2010-04-16

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Conducted to current accepted guidelines. No GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

yes

Remarks:

In place of centrifugation, the solution was filtered with filter paper prior to determination of the mass concentration of the substance in aqueous solution.

GLP compliance:

no

Type of method:

flask method

Water solubility:

2.4 g/L

Conc. based on:

test mat.

Temp.:

20 °C

pH:

7.7

Details on results:

In the first preliminary test, the sample remained essentially undissolved. At the end of the second preliminary test, the sample appeared totally dissolved. From the results of the preliminary testing, that the water solubility of calcium sulphate dihydrate was between 1 and 10 g per litre of water. In the definitive test, no tendency to concentration increase could be detected, so the average value of the 3 samples was taken to determine the solubility. It was observed that magnetic stirring increased the temperature slightly. During pH measurement, the temperature was measured from the filtrates allowing direct measurement during magnetic stirring. The temperature of the samples was found to increase from 20 to 21-22°C, which was not thought to produce noticeable effects on the solubility of the test material.

  Table 1: tabulated water solubility data

Sample	Ca in g/L		SO4 in g/L		pH
	Measurements	Mean value	Measurements	Mean value
Flask 1	0.724	0.725	1.911	1.9	7.7
	0.729		1.913		7.7
	0.723		1.9		7.6
Flask 2	0.731	0.728	1.873	1.86	7.7
	0.723		1.854		7.6
	0.729		1.881		7.6
Flask 3	0.724	0.723	1.735	1.73	7.7
	0.724		1.724		7.6
	0.721		1.719		7.7

The water solubility was determined from the concentration of calcium as the value calculated by using the solubility of SO4 instead of Ca produces a slightly higher value, this is due to a small interference by small quantities of sodium, potassium, magnesium sulfates explaining this small overestimation.

Conclusions:

The water solubility of CaSO4 was determined to be 2.4 g/L at 20°C and with a pH value of 7.7.

Description of key information

The water solubility of CaSO4 was determined to be 2.4 g/L at 20°C and with a pH value of 7.7.

Key value for chemical safety assessment

Water solubility:

2.4 g/L

at the temperature of:

20 °C

Additional information

The key study was performed to OECD 105 (non-GLP). It is supported by several literature and handbook data showing the solubility to be in the range of 2.34 -2.75 g/L at 20 -25°C.