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 [[_TOC_]]
 
+## Disclaimer
+I am no where near qualified enough to claim these notes are accurate. When in doubt, take the waste material to your local disposal.
+
 ### Sodium metasilicate
+Safe to mix with water and pour down the drain as far as I can find.
+
+### Sodium hydroxide
+Can be neutralised with an acid, which we should have:
 
 ### Ferric chloride
+Besides deactivating the acid, there's also the issue of the copper dissolved in the spent ferric chloride which is detrimental to the environment.
 
-### Sodium hydroxide
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+These instructions were found on [[https://wiki.london.hackspace.org.uk/w/index.php?title=Project:Deactivating_a_ferric_chloride_solution&redirect=no]]. I've copied them here in case the site goes down:
+
+> **Example**
+>
+> A solution that was made with a packet of ferric chloride (FeCl3) crystals weighing 300 grams requires 222 grams of sodium hydroxide (NaOH) to be deactivated.
+>
+> After deactivation, the neutralised solution will contain iron hydroxide (Fe(OH)3) which is rust and sodium chloride (NaCl) which is common table salt.
+>
+> Both are innocuous and can be poured down the drain.
+>
+> **Method**
+>
+> Pour the spent ferric chloride solution in a plastic bucket - do not use metal buckets, add about 5 times its volume of water. Dissolve 222 grams of sodium hydroxide in about 3 litres of water.
+>
+> In a thin stream, add the sodium hydroxide solution to the ferric chloride and stir. Once it turns rust coloured it is ready to be discarded.
+>
+> If not discarded, on standing, the iron hydroxide will separate out at the bottom, while at the top, a crust of copper carbonate (CuCO3) will form due to the copper from etched circuits.
+>
+> The iron hydroxide at the bottom is a standard commercial pigment and can be separated off the solution and added to latex paint.
+>
+> **In Theory**
+>
+> Ferric chloride reacts with sodium hydroxide turning into ferric hydroxide and sodium chloride.
+>
+> FeCl3 + 3 NaOH → Fe(OH)3 + 3 NaCl
+>
+> The proportions are:
+>
+> 1 mole of FeCl3 which is 91,3g reacting with 3 moles of NaOH which is 120g.
+> 
+> The mass of 1 mole is obtained by adding together the atomic masses obtained from the periodic table of elements:
+> 
+> Iron (Fe) has the atomic mass of 55.8 (grams/mole) and Chlorine (Cl) has the atomic mass of 35,5 (grams/mole).
+> 
+> Ferric chloride (FeCl3) will then have the molecular mass of 55.8 * 1 + 35.5 * 3 = 162.3 g/mole.
+> 
+> To find how many moles are contained in 300 grams of ferric chloride the calculation is 300/162.3 = 1.85 moles of ferric chloride.
+> 
+> Conversely; Sodium (Na) ~ 23 g/mole, Oxygen (0) ~ 16 g/mole and Hydrogen (H) 1 g/mole totalling 40 grams per mole.
+> 
+> Each mole of FeCl3 requires 3 moles of NaOH (sodium hydroxide) at 40 grams per mole.
+> 
+> The weight of Na0H required to deactivate the spent FeCl3 solution is obtained thus:
+> 
+> 1.85 * 3 = 5.55 moles of NaOH, at 40 g/mole that will be 5.55 * 40 = 222 grams NaOH.
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