Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ordered Water

15.04.2009
Just how much water is there in calcined gypsum?

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).

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), mailto:michael.braeu@basf.com

Title: How Much Water Does Calcined Gypsum Contain?

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

Michael F. Bräu | Angewandte Chemie
Further information:
http://pressroom.angewandte.org

More articles from Life Sciences:

nachricht Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute

nachricht Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>