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VI. Platina with the eJJ'ential salts of urine.

From putrefied urine inspissated to the consistence of asyrup, is obtained by crystallization a singular saline con-crete, called the fusible or essential salt of urine, or micro-cosmic salt, containing the acid of phosphorus united witha volatile alcali. This salt, exposed to the fire, parts withits alcali, and assumes a gladly appearance; in which state,all the common metals, gold not excepted, are said to becorroded by it in fusion. A hundred and eighty grains ofthis fait were mixed with thirty grains of platina, and urgedin a crucible with a strong fire for two hours: the platinawas found unchanged at the bottom, covered with the salt,which likewise appeared little altered. Sixty grains ofthis salt, the same quantity of calcined borax, and thirtygrains of platina, were treated in the fame manner: therewas a vitreous scoria, somewhat opake, of a yellowishgreen colour: the salts and lighter parts being separatedby washing, the dried platina appeared of its natural form,but whiter than at first.

After the crystallization of the foregoing salt from urine,there crystallizes another, not containing the phosphorineacid, and whose composition is as yet unknown. Threedrams of this fait and half a dram of platina being urgedwith a strong fire in a close crucible, the salt run ailthrough the crucible, and the platina, alter rubbing in amortar and washing with water, appeared in its originalform, being only somewhat whiter than before. A dramof the salt, a dram of calcined borax, and a dram of pla-tina, treated in the same manner, gave a green-yellowiih,dark-chrysoiite-colourcd vitreous mass, under which l^ythe platina unaltered, except that as in the former cafe itwas whiter than at first. All these experiments are iron*.Marggraf.

VII. Platina