For the heating of concentration plants, an eutectic blend of KNO3 + NaNO2 + NaNO3 has given good results in the practice, as a heat transfer compound for high temperatures. The above composition gives a heat transfer salt which works adequately well within a relatively broad temperature range of approx. 160-500°C. The corrosion tendency of this salt is very low on heat resistant steel type 15 Mo 3 under 490°C and CrNi type steel under 550°C.