Note 12 — Chapter XX · SULPHUR, SELENIUM, AND TELLURIUM

In the formation of potassium sulphide, K2S (that is, in the combination of 32 parts of sulphur with 78 parts of potassium), about 100 thousand heat units are developed. Nearly as much heat is developed in the combination of an equivalent quantity of sodium; about 90 thousand heat units in the formation of calcium or strontium sulphide; about 40 thousand for zinc or cadmium sulphide, and about 20 thousand for iron, cobalt, or nickel sulphide. Less heat is evolved in the combination of sulphur with copper, lead, and silver. According to Thomsen, sulphur develops heat with hydrogen in solutions. The reaction I2,Aq,H2S = 21,830 calories. But, as the reaction I2 + H2 + Aq develops 26,842 calories, it follows that the reaction H2 + S develops 4,512 calories.