Pigments through the Ages - Manufacture Recipes

How Cobalt yellow is made:

Artificial variety of pigment	Reaction of cobaltous salts with acetic acid and subsequent mixing with concentrated solution of potassium nitrite.

In the lab
Materials needed:	Cobalt(II)-chloride (CoCl₂· 6H₂O), potassium nitrite (KNO₂), acetic acid
Safety (MSDSs):	Cobalt(II) chloride, potassium nitrite, acetic acid (at Fisher Scientific)
Method:	1 g of cobalt(II)-chloride is solved in 20 ml of deionized water and acidified with approximately 1 ml concentrated acetic acid. 8 g potassium nitrite is then solved in 20 ml of deionized water and slowly added to the cobalt chloride solution. The resulting precipitate is washed and filtered off.

Making cobalt yellow in the lab


The acidified solution of potassium nitrite is poured into the solution of cobalt(II) chloride	The precipitation of cobalt(II) potassium nitrite is being filtered off