Sodium carbonate
Burgundy mixture is made by combining dissolved copper sulphate and dissolved sodium carbonate. Dissolved copper sulphate ratios generally range from 1:1 to 1:18. Sodium carbonate is generally added in higher quantities and at a dissolved ratio of 1:1.5. Over time, the sodium carbonate will crystallize out of solution, and the closer the copper sulphate to carbonate mixture is to 1:1 ratios, the faster this process occurs. This property is one key factor in the general discontinued usage of Burgundy mixture, as the mixture must be mixed shortly before intended utilization.