C2I15  as a colourless spontaneously inflammable

gas of unbearable smell . Boron triethyl B(C2H5)3 is obtained in the same manner, by using zinc ethyl . It is a colourless spontaneously inflammable liquid of boiling point 95° C . By the action of one molecule of ethyl borate on two molecules of zinc ethyl, the compound B(C2H3)2.002I-I5 diethylboron ethoxide is obtained as a colourless liquid boiling at 'of C . By the action of water it is converted into B(C2H5)2.OH, and this latter compound on exposure to air takes up oxygen slowly, forming the compound B•C2H5.002H5.OH, which, with water, gives B(C2Hz)•(OH)2 . From the condensation of two molecules of ethyl borate with one molecule of zinc ethyl the compound B2•C2H5 . (OC2H5)5 is obtained as a colour-less liquid of boiling point 112° C . Boron triethyl and boron trimethyl both combine with ammonia . The atomic weight of boron has been determined by estimating the water content of pure borax (J . Berzelius), also by conversion of anhydrous borax into sodium chloride (W . Ramsay and E . Aston) and from analysis of the bromide and chloride(Sainte-Claire Deville) ; the values obtained ranging from 10.73 to 11.04 .

Boron can be estimated by precipitation as

potassium fluoborate, which is insoluble in a mixture of potassium acetate and alcohol . For this purpose only boric acid or its potassium salt must be present; and to ensure this, the borate can be distilled with sulphuric acid and methyl alcohol and the volatile ester absorbed in potash .