Arcanum duplicatum

Potash Sulphate of Potash 2 Fixed vegetable alkali Vitriolated tartar Sel de duobus Arcanum duplicatum... 

Potassium Sulfate (Sal polychrestum, Arcanum duplicatum or Tartarus vitriolatus). K2S04 mw 174.26 color , odorless, hard, bitter tasting cryst mp 1067° d 2.66g/cc. Sol in w insol in ethanol. CA Registry No [7778-80-5]. Prepn is by reacting K hydroxide with sulfuric add (Ref 12)... 

Arcanum duplicatum Caswell No. 702 Dipotassium sulfate EINECS 233-558-0 EPA Pesticide Chemical Code 005603 Glazier s salt HSDB 6047 Kalium sulphuricum Potassium sulfate Potassium sulphate Sal Polychrestum Sulfuric acid, dipotassium salt Sulphuric acid, potassium salt Tartarus vitriolatus. Analytical reagent, medicine (cathartic), gypsum cements, fertilizer, manufacture of alum and glass, food additive. Registered by EPA as a herbioide and insecticide. Colorless, hard crystals, mp = 1067° d = 2.66 soluble in H2O (12 g/100 ml at 25°, 25 g/100 ml at 100°),... 

Potassium sulfate (poe-TAS-ee-yum SUL-fate) is also known as potash of sulfur, sulfuric acid dipotassium salt, arcanum duplicatum, and sal polychrestum. It is a colorless or white granular, crystalline, or powdery solid with a hitter, salty taste. It occurs in nature as the mineral arcanite and in the mineral langheinite (K2Mg2(S04)3). The compound was known to alchemists as early as the fourteenth century, and was analyzed hy a number of early chemists, including Johann Glauber (1604-1670), Robert Boyle (1627-1691), and Otto Tachenius (c. 1620-1690). 

Rouelle showed that in addition to neutral arcanum duplicatum (sulphate of potash), a compound of acid and alkaline salts (i.e. acid and alkali Rothe did not call these salts ), an acid sulphate (potassium hydrogen sulphate, KHSO4) can be obtained by heating the neutral sulphate with sulphuric acid, and he instanced other cases. He emphasised that there is true combination (combinaison) between the parts of acid salts, and although Baume maintained that they were only mixtures, Rouelle s point of view was defended by Bayen (1774-5) basic salts of mercury, and by Bergman (1775) ... 

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