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Spectacular Breeding of Crystals on Silica Gel

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Ryszard Piekos and Jacek Teodorczyk

Department of Inorganic Chemistry, Faculty of Pharmacy, Medical University of Gdansk, PL-80-416 Gdansk, Poland

J. Chem. Educ., 2005, 82 (3), p 448

DOI: 10.1021/ed082p448

Publication Date (Web): March 1, 2005

Section:

History, Education, and Documentation

Abstract

During experiments with silicic acid sols blended with thiosulfate solutions, an interesting phenomenon was observed. Namely, after gelation of the systems and evaporation of excessive water at ambient temperature, the gels cracked and on their surface grasslike offsprings appeared, which continued to grow. A closer inspection of these species showed them to be sodium thiosulfate, slightly less hydrated than the parent salt (pentahydrate). A literature search for explanation of this phenomenon led the authors to a class of minerals known as antholytes, whose representative is a rare mineral chalcanthite, CuSO₄•5H₂O. Further experiments with CuSO₄•5H₂O, Cr₂(SO₄)₃•18H₂O, Al₂(SO₄)₃•18H₂O, NiSO₄•7H₂O, Na₂SO₄•10H₂O, and (NH₄)₂SO₄ gave similar results. With colorful salts, the ”antholytes“ differed in hydration degree and morphology of crystals as compared to those of the parent salts. These experiments are particularly recommendable for undergraduate students for demonstration of several reactions and phenomena such as preparation of silicic acids by ion-exchange from sodium metasilicate, sol–gel transition, aging of silica gels, preparation of antholytes, and demonstration of the labile nature of monosilicic and thiosulfuric acids.

Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Inorganic Chemistry

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Crystals / Crystallography

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Biocatalysis with Sol−Gel Encapsulated Acid Phosphatase
Suhasini Kulkarni, Vu Tran, Maggie K.-M. Ho, Chieu Phan, Elizabeth Chin, Zeke Wemmer and Monika Sommerhalter
Journal of Chemical Education2010 87 (9), 958-960
- Biocatalysis with Sol−Gel Encapsulated Acid Phosphatase
  Suhasini Kulkarni, Vu Tran, Maggie K.-M. Ho, Chieu Phan, Elizabeth Chin, Zeke Wemmer and Monika Sommerhalter
  Journal of Chemical Education2010 87 (9), 958-960
  This experiment was performed in an upper-level undergraduate biochemistry laboratory course. Students learned how to immobilize an enzyme in a sol−gel matrix and how to perform and evaluate enzyme-activity measurements. The enzyme acid phosphatase (APase)...
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