Potassium dichromate

Particle size distribution (Granulometry)

Administrative data

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Modern study conducted under GLP to the appropriate guidelines.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 110 (Particle Size Distribution / Fibre Length and Diameter Distributions)

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: DIN ISO 4497

Principles of method if other than guideline:

A dry sieve test according to DIN ISO 4497 will be performed to separate the bigger particles (>1 mm) from smaller particles and the particulate matter (<100 µm). The particulate matter will then be tested according to OECD 110 particle size distribution by laser diffraction.

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Potassium dichromate

EC Number:

231-906-6

EC Name:

Potassium dichromate

Cas Number:

7778-50-9

Molecular formula:

K2Cr2O7

IUPAC Name:

sodium dichromate

Details on test material:

The test material was obtained from JSC Aktyubinsk Chromium Compounds Plant.

Results and discussion

Particle size

Percentile:

D50

Remarks on result:

other: Migrated from fields under 'Mass median diameter' as D50 percentile. No source field for Standard deviation.

Particle size distribution at different passages

Particle size distribution at different passages 1

No.:

#1

Size:

> 1 mm

Distribution:

< 0.01 %

Particle size distribution at different passages 2

No.:

#2

Size:

> 0.1 - < 1 mm

Distribution:

99.3 %

Particle size distribution at different passages 3

No.:

#3

Size:

< 100 µm

Distribution:

0.5 %

Particle size distribution at different passages 4

No.:

#4

Size:

< 10 µm

Distribution:

0.003 %

Particle size distribution at different passages 5

No.:

#5

Size:

< 1 µm

Distribution:

0 %

Any other information on results incl. tables

The sample was sieved manually using two sieves with a mesh size of 1 mm and 100 µm, respectively. The three resulting fraction were quantified gravimetrically and are tabulated below.

Fraction no.	Particle fraction	Weight	Amount in % of the test item
1	Share bigger than 1 mm	Not detectable	<0.01%
2	<1 mm but bigger than 100 µm	99.03 g	98.3%
3	Particulate matter (<100 µm)	1.4811 g	1.5%
Total			99.8%

The particulate matter was further evaluated using laser diffraction. The test item was dispersed in ethanol and measured by laser diffraction. For calculation of the particle size distribution, the Fraunhofer model was used.

Particle fraction	Amount in % of dry sieve fraction 3
Particulate matter >100 µm	65.49%
Particulate matter (<100 µm)	34.3%
Particulate matter (<10 µm)	0.21%
Particulate matter (<1 µm)	Not detectable

This result (sum of mass bigger than 100 µm = 65.49%) is in contradiction with the dry sieve test. Therefore fraction 3 of the dry sieve test was investigated by microscopy and sieved again. The microscopic picture reveals particles which are bigger than 100 µm and which are rod shaped. Therefore the laser diffraction is verified.

A second dry sieve test was performed and no particles bigger than 100 µm. These particles must have passed the sieve although bigger than 100 µm due to their rod-shape.

Using this data, the share of fraction 3 of the original dry sieve test will be split and the share bigger than 100 µm added to fraction 2 of the first dry sieve test. The particle size distribution is therefore:

Particle fraction	Method	Amount in % of dry sieve fraction 3
Share bigger than 1 mm	Dry sieve test	<0.01%
<1 mm but bigger than 100 µm	Dry sieve test corrected by laser diffraction	99.3%
Particulate matter (<100 µm)	Laser diffraction of dry sieve fraction 3	0.5%
Particulate matter (<10 µm)	Laser diffraction of dry sieve fraction 3	0.003%
Particulate matter (<1 µm)	Laser diffraction	Not detectable

Applicant's summary and conclusion

Conclusions:

The particle size distribution was found to be <0.01% particles bigger than 1 mm, 99.3% of particles <1 mm and >100µm, <0.5% of particulate matter (<100µm) and 0.003% of particulate matter (<10 µm).

Executive summary:

The particle size distribution was determined using two test methods; a dry sieve test according to DIN ISO 4497 and a laser diffraction test of the particulate matter according to OECD 110. The particle size distribution was found to be <0.01% of particles bigger than 1 mm, 99.3% of particles <1 mm and >100µm, <0.5% of particulate matter (<100µm) and 0.003% of particulate matter (<10 µm).