MadSci Network: Chemistry

Re: recipe for sodium silicate solution/water glass

Date: Sat Jun 19 00:58:34 1999
Posted By: Jonathan Feldman, Undergraduate, Applied Chemistry, University of Western Sydney
Area of science: Chemistry
ID: 929111690.Ch

Hi Irene

Regarding your request for a sodium silicate recipe, according to what I have found, all you need to do is dissolve your sodium silicate powder in water. However, it may take a while to dissolve, so patience, and a lot of stirring may be necessary. Varying the amount of sodium silicate will also vary the viscosity, so adjust it to your needs.

This should be satisfactory for your students to use in chemical gardens. I'm not sure if you already know how to make chemical gardens, but it is here for your (and your students) benefit anyway:

Take some various different metal salts, and drop them into your waterglass solution.

As each crystal dissolves, it reacts with the sodium silicate to form a bubble of material with a silicate "skin". E.g., if you use copper chloride, the skin will be copper silicate. This skin is porous, and as the pressure of the water inside the bubble increases, it will burst at the top, and a new bubble forms. This repeated action forms columns, which are your "plants" in the "garden".

Each different salt should give the characteristic colour of that metal, so your copper salt columns should be blue, nickel - green, cobalt - pink, etc.

I assume the columns will be fairly fragile, so it would be important not to disturb it while it is growing.

I haven't had a chance to try this experiment myself, so I can't guarantee anything, but I would be interested if you could let me know how well it works.

Perhaps you could have your students make a big garden in a fishbowl or similar, and put it on display in your school.

I hope this has been of assistance,

Jonathan Feldman, UWS Nepean

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