What toxic gases are emitted during the combustion of potassium ferrocyanide?
Potassium ferrocyanide cannot burn, because it is the product of a combustion. When meat or blood is overheated, carbonized and burnt, the remaining ashes contain potassium ferrocyanide. And this product was initially recovered by washing these ashes and evaporating the obtained solution. In German, this compound is called Blutlaugensalz, which means &quot;salt from washing blood&quot; This is even the way this product was originally discovered in the old times of beginning chemistry.
So potassium ferrocyanide resists high temperature, and will not produce any $\ce{HCN}$ by heating or by combustion. The only way of producing HCN out of it, is to heat it with diluted sulfuric acid, according to the equation : $$\ce{K4Fe(CN)6 + 3 H2SO4 -&gt; 2 K2SO4 + FeSO4 + 6 HCN}$$This reaction is difficult to carry out properly, because, if the sulfuric acid is more concentrated, it will destroy $\ce{HCN}$ according to  $$\ce{H2SO4 + 2 HCN + 2 H2O -&gt; (NH4)2SO4 + 2 CO}$$