A chemical garden

I found this activity in an old report from CHEM ED 95 and I was struck by how old this experiment was. This experiment was done by Glauber about 1650.

Dissolve 190 g of sodium silicate (water glass) in 190 cm³ of distilled water. On the bottom of a two-litre beaker, place well-spaced crystals of nickel chloride, cobalt chloride, manganese(II) sulphate, copper sulphate and iron(II) sulphate.¹ Carefully add the water glass solution to the beaker containing the crystals. The films of these insoluble silicates form semipermeable membranes.

Serendipitously, a neat little video² showing crystals growing in sodium silicate solution was recently tweeted by William Barron de Burgh, a teacher at Dame Elizabeth Cadbury School, Birmingham, UK. The video captures the iron(III) chloride added to water glass in real time. I highly recommend this video and activity. William also posted a couple of photos of his crystal garden. 

A crystal garden by William Barron de Burgh

 References

1. Unfamiliar with this old favourite? Try B.Z. Shakhashiri, Chemical Demonstrations: A Handbook for Teachers of Chemistry, Volume 3, 1990, page: 379
2.  Video of crystal garden posted by @WRBdB 

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     [JLH]