Cobalt complexes demo, modified to avoid use of 12M HCl
(see below, variation of Fall 2007)
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See safety, disposal, and additional information 
	Shakhashiri Vol. 1 p. 280

Starting materials:

4x (A,B,C,D) 300ml test tubes in rack
	A,B,C -	contain 50ml each 0.1M CoCl2
	D     -	contains ~100 ml water (or wait for demo step 3)

3x (a,b,c) Grad. cyl (50,100,250 ml sizes)
	a - contains  50ml 6M CaCl2
	b - contains 100ml 6M CaCl2
	c - contains 150ml 6M CaCl2

3x (D,E,F) 100ml test tubes in rack

Hot plate water bath at b.p.
Cold water bath at ice temperature
	suggest 1000ml TF beakers for water baths

Suggest backlighting and digital thermometer
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Demo procedure:

1) with swirling, add a to A, b to B, and c to C 
note colors

2) divide B+b approximately equally among D,E,F
	D to cold bath, 
	E to hot bath, 
	F remains ambient temperature
note colors

3) with swirling, add C+c to D (dilutes C+c)
note color change

Rev. 20050725 LCM 

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Variation of Fall 2007 (Prof. Boering)

DEMO: Pink to blue
Place 20 parts of 0.10 M CoCl2 in a container. Add 5 parts saturated CaCl2.
Record the color. Repeat until the solution is blue.

Write the ionic equation: 
[Co(H2O)6 ]2+ (aq) +  2CaCl2    R    [CoCl4]2- (aq) +   2Ca 2+ + 6H2O

THEN
DEMO: Blue to pink
Add water to reverse the reaction.\

Rev. 20070920

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Variation of Fall 2007 (Prof. Majda)

Demo: Pink to Blue

Add 50mL of CoCl2 (0.1M) to each of 4 large reaction tubes. 
The first, viewers' leftmost, is the "standard," unreacted starting material.

To the other 3 tubes:

Tube 2:  Add  50mL of HCL (9M) to the 50mL CoCL2.  
Tube 3:  Add 100mL of HCL (9M) to the 50mL CoCl2.
Tube 4:  Add 150mL of HCL (9M) to the 50mL CoCL2.   

Color should go from Pink -> Purple -> Blue