Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Ordered Water: Just how much water is there in calcined gypsum?

Abstract:
Gypsum was used as a building material in antiquity and is still widely used as a binder in plaster, drywall, and spackling paste. Known as dihydrate in construction chemistry, gypsum is a water-containing calcium sulfate (CaSO4. 2 H2O).

Ordered Water: Just how much water is there in calcined gypsum?

Trostberg, Germany | Posted on April 16th, 2009

In various calcination processes, some of the water of crystallization is removed, resulting in calcined gypsum, or hemihydrate (CaSO4. 0.5 H2O). When this material comes into contact with water, it reabsorbs it and sets up. The structure and exact water content of hemihydrate have remained a matter of speculation.

Michael F. Bräu (BASF Construction Chemicals GmbH) and Horst Weiss (BASF SE) have now brought this speculation to an end: by using single-crystal structural analyses they were able to solve the structure, generate a structural model, and support it with computer calculations. As reported in the journal Angewandte Chemie, hemihydrate does indeed contain exactly one half of a water molecule per structural unit—tightly bound to the calcium sulfate framework.

Hemihydrate is the most heavily produced inorganic compound worldwide, so its structure and water content are of great interest, both economically and scientifically. The first structural model of this compound was proposed in 1933, and it still holds today. Since then, there have been a number of refined models, which do a good job of reproducing the fundamental calcium sulfate scaffold. However, there has always been disagreement about whether the water molecules also adopt a defined arrangement and if so, what it looks like.

Answering such questions requires structural analyses based on X-ray diffraction experiments carried out on single crystals of the right size and quality. The atoms of a crystal deflect incoming X-rays; the resulting characteristic diffraction pattern makes it possible to calculate the positions of the individual atoms in the crystal. However, this has been very difficult to achieve in the case of gypsum crystals. Bräu and Weiss have now been successful. By using various tricks they were able to interpret the diffraction pattern and to use their computer calculations to consolidate the data into a plausible structural model. The alignments of the individual water molecules and their distances from each other prove that there are no interactions between them; they are bound only to the calcium sulfate framework. They are packed in so tightly that no further water molecules can enter into the channels of the basic structure. Variations of the crystal with a proportion of water molecules above 0.5 per formula unit thus seem to be very unlikely.

Author: Michael F. Bräu, BASF Construction Chemicals GmbH, Trostberg (Germany),

Title: How Much Water Does Calcined Gypsum Contain?

Angewandte Chemie International Edition 2009, 48, No. 19, 3520-3524, doi: 10.1002/anie.200900726

####

Copyright © Angewandte Chemie

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Nanoparticles Increase Durability of Concrete Decorations in Cold Areas January 26th, 2015

Iranian Researchers Boost Solar Cells Efficiency Using Anti-Aggregates January 26th, 2015

Detection of Heavy Metals in Samples with Naked Eye January 26th, 2015

Engineering self-assembling amyloid fibers January 26th, 2015

Chemistry

Anti-microbial coatings with a long-term effect for surfaces – presentation at nano tech 2015 in Japan January 21st, 2015

Hydrogels deliver on blood-vessel growth: Rice researchers introduce improved injectable scaffold to promote healing January 20th, 2015

Graphene enables all-electrical control of energy flow from light emitters: First signatures of graphene plasmons at telecommunications wavelength revealed January 20th, 2015

Nanotechnology Used to Produce Ceramic Membrane with High Thermal Stability January 19th, 2015

Announcements

Nanoparticles Increase Durability of Concrete Decorations in Cold Areas January 26th, 2015

Iranian Researchers Boost Solar Cells Efficiency Using Anti-Aggregates January 26th, 2015

Detection of Heavy Metals in Samples with Naked Eye January 26th, 2015

Engineering self-assembling amyloid fibers January 26th, 2015

Water

Nanoparticles for clean drinking water January 17th, 2015

Going with the flow January 16th, 2015

Rice's Naomi Halas to direct Smalley Institute: Optics pioneer will lead Rice's multidisciplinary science institute January 15th, 2015

Liquids and glasses relax, too. But not like you thought January 15th, 2015

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE