Aluminum sulfate

Structural formula
${\displaystyle \mathrm {\ {\Biggl [}} }$ ${\displaystyle \mathrm {\ \!\ {\Biggr ]}_{2}} }$ ${\displaystyle \mathrm {\ {\Biggl [}} }$ ${\displaystyle \mathrm {\ \!\ {\Biggr ]}_{3}} }$
General
Surname	Aluminum sulfate
other names	Sulfuric acid clay E  520 ALUMINUM SULPHATES ( INCI )
Molecular formula	Al 2 (SO 4 ) 3
Brief description	colorless crystals
External identifiers / databases
CAS number 10043-01-3 (anhydrous) 17927-65-0 (hydrate unspecified) 16828-11-8 (16-hydrate) 7784-31-8 (18 hydrate) EC number 233-135-0 ECHA InfoCard 100.030.110 PubChem 24850 ChemSpider 23233 DrugBank DB11239 Wikidata Q421857
properties
Molar mass	342.13 g mol −1
Physical state	firmly
density	2.71 g cm −3
Melting point	770 ° C (decomposition)
solubility	easy in water (360 g l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 318 P: 280-305 + 351 + 338
MAK	6 mg m −3 (Al)
Thermodynamic properties
ΔH f 0	−3442 kJ mol −1
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Aluminum sulfate

Aluminum sulfate , empirical formula Al ₂ (SO ₄ ) ₃ , is a chemical compound of aluminum from the group of sulfates . It forms a colorless powder with a density of 2.71 g / cm ³ .

Occurrence

In nature, for example, aluminum sulfate occurs in the mineral alunogen . It can also be obtained from naturally occurring alums .

synthesis

The hydrate of aluminum sulfate can be obtained by dissolving pure aluminum oxide or aluminum hydroxide in concentrated sulfuric acid .

${\displaystyle \mathrm {2\,Al(OH)_{3}+3\,H_{2}SO_{4}\longrightarrow Al_{2}(SO_{4})_{3}+6\,H_{2}O} }$

Responsiveness

With an acidic reaction, aluminum sulfate dissolves in water and crystallizes out as monoclinic Al ₂ (SO ₄ ) ₃ · 18 H ₂ O at room temperature . From a temperature of 340 ° C, the salt is completely dehydrated and above 770 ° C it breaks down into aluminum oxide and sulfur trioxide .

Aluminum sulfate forms double salts with the sulfates of monovalent metals according to the following formula (alums):

${\displaystyle {\mbox{M}}^{I}{\mbox{Al}}({\mbox{S}}{\mbox{O}}_{4})_{2}\cdot 12\,{\mbox{H}}_{2}{\mbox{O}}}$

use

Aluminum sulfate has the following uses:

• Retention aids and for sizing in paper manufacture
• Flocculants in drinking water treatment
• Mordants in dyeing
• Seed dressing
• Part of foam extinguishing agents
• Flame retardants
• Insulating salt (on fresh cement or lime substrates, against water and nicotine stains) in the renovation
• Ingredient in plant strengtheners and protection agents and for the blue coloration of hydrangeas
• Firming agent or stabilizer in food, approved as food additive E 520 in the EU .

Accidents and health hazards

In an incident with aluminum sulphate in drinking water at Camelford , Cornwall, England, in July 1988, a number of people drank drinking water with higher concentrations of aluminum sulphate. The permissible limit values ​​were exceeded 5000 times. After the accident, numerous residents complained of ulcers, rashes and memory problems, among other things. A death in 2006 intensified a debate about the long-term effects of the accident. Studies of the long-term health effects following this incident are still not fully completed, but post-mortem studies found particularly high levels of aluminum in the victims' brains and further studies have been commissioned to see if there is an association with cerebral amyloid angiopathy .

In 2013, aluminum sulfate was included in the EU's ongoing action plan ( CoRAP ) in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation . The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. The reasons for the uptake of aluminum sulphate were concerns about consumer use , high (aggregated) tonnage, high risk characterization ratio (RCR) and widespread use, as well as the dangers arising from a possible assignment to the group of CMR substances and the possible risk sensitizing properties. The re-evaluation has been running since 2015 and is carried out by France . In order to be able to reach a final assessment, further information was requested.

Name alum

In a chemically incorrect manner, papermakers refer to aluminum sulfate as alum.

Individual evidence

1. ↑ Entry on E 520: Aluminum sulphate in the European database for food additives, accessed on June 27, 2020.
2. ↑ Entry on ALUMINUM SULPHATES in the CosIng database of the EU Commission, accessed on February 13, 2020.
3. ↑ ^{a b c d} Entry on aluminum sulfate. In: Römpp Online . Georg Thieme Verlag, accessed on December 25, 2014.
4. ↑ ^{a b c d} Entry on aluminum sulfate in the GESTIS material database of the IFA , accessed on February 1, 2016(JavaScript required) .
5. ↑ ^{a b} Data sheet aluminum sulfate (anhydrous) from AlfaAesar, accessed on January 31, 2010 ( PDF )(JavaScript required) .
6. ↑ PAETEC Formula Collection Edition 2003, p. 116.
7. ↑ Article on the use of aluminum sulfate as a flame retardant in insulation made from renewable raw materials on EnBauSa.de; accessed in Sept. 2016
8. ↑ Market overview - Insulation materials made from renewable raw materials from the specialist agency for renewable raw materials, see table on p. 29; accessed in September 2016
9. ↑ Federal Office for Consumer Protection and Food Safety: Declaration of active ingredients that are contained as co-formulants in plant protection products. ( Memento of December 8, 2015 in the Internet Archive ) (As of December 1, 2009).
10. ↑ Poisoned: The Camelford scandal. The Independent , April 16, 2006, accessed March 30, 2011 . 
11. ^ Nigel Hawkes: Alzheimers linked to aluminum pollution in tap water . In: The Times , April 20, 2006. Retrieved April 7, 2010. 
12. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): Aluminum sulphate , accessed on March 26, 2019.
13. ↑ Taschenbuch der Papiertechnik , Jürgen Blechschmidt, Carl Hanser Verlag GmbH & Co. KG, 2010 e ISBN 978-3-446-42322-0 Print ISBN 978-3-446-41967-4 https://doi.org/10.3139/ 9783446423220