454 Dr. A. Schrauf on Molybdates and Vanadates of Lead. [May 4, 



intense. Wulfenite, even when used in fragments ten times larger, loses 

 its colour and becomes white in far shorter time. 



If a splinter of eosite is dissolved in a drop of slightly heated hydrochloric 

 acid, the solution spread on a glass plate, some alcohol added to it, and 

 the whole again heated to dryness*, a bluish deposit, somewhat verging 

 into greenish grey, is obtained. With respect to the quantity of eosite 

 experimented upon, and to the extent of the deposit, its tint may be consi- 

 dered as of medium intensity; it is bordered on its margin by a delicate green, 

 somewhat acicular precipitate. Fragments of yellow wulfenite, vanadinite, 

 or red chromate of lead, of equal size and treated in the same way, give 

 different deposits on the glass plate, — wulfenite a deep blue one (on ac- 

 count of the formation of molybdate of molybdenum), vanadinite a yellowish 

 or bluish-green one, and crocoite a feeble yellowish-green onef. The 

 crystals of eosite being of scarce occurrence and of diminutive size, only 

 few experiments could be made concerning the action of the blowpipe on 

 them. 



Eosite, when heated in a glass tube, assumes a darker tint without 

 decrepitating, and, when cooled, takes again its original colour. A splinter 

 of this mineral, mixed with three times its volume of bisulphate of potash 

 and fused on platinum-foil, gives under a glowing heat a transparent, 

 nearly colourless saline mass with a very slight light-yellow tint. During 

 its cooling, this mass becomes for a moment reddish brown, and, after 

 complete cooling, assumes a light orange-brown tint. 



Comparative experiments made with chromate, vanadate, and molybdate 

 of lead, as also with binary mixtures of the powders of these three sub- 

 stances, proved the colour of the eosite salt to approach very nearly the 

 tint of the saline mass obtained by fusing a mixture of two to three 

 parts of molybdate of lead and one part of vanadate of lead with bisul- 

 phate of potash. 



The substance obtained by fusing eosite with bisulphate of potash, 

 brought into contact with water in a platinum spoon, gives a solution 

 which, some tin-foil being added to it and the whole being brought to 

 ebullition J, assumes a faint greenish-blue tint. A second experiment gave 

 the same result, and proved the solution to give, when further evapo- 

 rated, a yellowish-brown residuum — possibly caused by the presence of 



* It must be remarked that all these experiments have been made under the micro- 

 scope, or, at least, under a powerful magnifying-lens, so that it was impossible to sepa- 

 rate the chloride of lead from the solution containing molybdenum. 



t As M. Czudnowicz has stated (Poggendorff' s Ann. vol. cxx. p. 17), the action of 

 alcohol on the hydrochloric solution of vanadium gives rise to precipitates tinted between 

 blue or brown, according to the degree of oxidation. I also obtained at first, by mixing 

 with alcohol a solution of vanadate of lead, precipitates changing from yellowish green 

 into brown, according to the degree of heat. The exact and constant temperature for 

 the evaporation of alcohol was, however, soon ascertained by a series of experiments. 



\ The splinters of eosite submitted to chemical action being scarcely £ millim. in 

 size, the chloride of lead could not be isolated. 



