ERYTHRITE  , the name given to (I) a

mineral composed of a hydrated cobalt arsenate, nd (2) in chemistry, a tetrahydric alcohol . (I) The mineral erythrite has the formula Co3(AsO4)2.8H2O, and crystallizes in the monoclinic system and is isomorphous with vivianite . It sometimes occurs as beautiful radially-arranged groups of blade-shaped crystals with a bright crimson colour and brilliant lustre . On exposure to light the colour and lustre deteriorate . There is a perfect cleavage parallel to the plane of symmetry, on which the lustre is pearly . Cleavage flakes are soft (H=2), sectile and flexible; specific gravity 2.95 . The mineral is, however, more often found as an earthy encrustation with a peach-blossom colour, and in this form was early (1727) known as cobalt-bloom ( Ger . Kobaltbliithe) . The name erythrite, from ipv0pbs, " red," was given by F . S . Beudant in 1382 . Erythrite occurs as a product of alteration of smaltite (CoAs2) and other cobaltiferous arsenides .

The finest crystallized specimens are from

Schneeberg in Saxony . The earthy variety has been found in Thuringia and Cornwall and some other plates . (2) The alcohol erythrite has the constitutional formula HO•H2C•CH(OH)•CH(OH)•CH2OH; it is also known as erythrol, erythroglucin and phycite . It corresponds to tartaric acid, and, like this substance, it occurs in four stereo-isomeric forms . The internally compensated modification, i-erythrite, corresponding to mesotartaric acid, occurs free in the algae Protococcus vulgaris, and as the orsellinate, erythrin, C4H6(OH)2(O•C8H203)2, in many lichens and algae, especially Roccella montagnei . It has a sweet taste, melts at 126°, and boils at 330 . Careful oxidation withdilute nitric acid gives erythrose or tetrose, which is probably a mixture of a trioxyaldehyde and trioxyketone . Energetic oxidation gives erythritic acid and mesotartaric acid. i-Erythrite and the racemic mixture of the dextro and laevo varieties were synthesized by Griner in 1893 from divinyl .