{ 



86 ' W. Gihbs and F. A. Genth 



1. Sandstones and cla3^s, wbite, gray or brown, in irregtilar 

 and unequal alternating beds; containing few fossils except frag* 

 ments of carbonized wood. 



I can therefore only regard the sandstone of the southwest, or 

 at least a large part of it, as identical in age, and a prolongation 

 of the formation 'No. 1 of Nebraska; and which from the evi- 

 dence of its cretaceous character, and the absence of any evi- 

 dence to the contrary, must be referred to the cretaceous period. 



—^4. 



Abt 



Bases : bv WoL 



A. Genth. Part I. 



Concluded from vol. xxiii, p. 841. 



XAXTHOCOBALT. 



The salts of Xanthocobalt may be prepared by two distinct 

 processes, either directly from ammoniacal solutions of salts of 

 cobalt, or from neutral, acid, or ammoniacal solutions of the salts 

 ' of Roseocobalt or Purpureocobalt. In any case, the gas arising 

 from the action of nitric acid upon starch or saAvdust, and which 

 may be considered as a mixture of CO2, NO2, KO3, and NO 4 

 the last probably in excess — is to be passed into the solution, 

 A more or less rapid absorption accompanied by copious fumes 

 of carbonate of ammonia takes place. The color of tlie liquid 

 gradually changes to a dark reddish-brown or dark sherry -wine 

 color, and the liquid on cooling generally deposits an abundance 

 of a salt of Xanthocobalt in brown-yellow crystals. When a 

 current of the red gas above mentioned, and which we shall de- 

 note by the symbol NOx, is passed into an acid solution of cobalt 

 and ammonia, an absorption also usually takes place, but in this 

 case no Xanthocobalt is produced, but only a beautiful yellow 

 crystalline salt, which is the ammonia nitrite of cobalt, corres- 

 ponding to the yellow potash salt, first described by Fischer,* 

 some years afterward re-discovered and analyzed by St. Evre,t 

 and finally examined by Stromeyer.:}; The formation of this 

 compound is easily prevented, by keeping the solution ammoni- 

 acal by constant additions of ammonia. " 



* Pogg. "Ann., Ixxiy, 115, and Ixxxviii, 496. 



+ Compt. Rend., xxxiv, 479, and Ann. de Chimie et de Phys^iqnc, xxxviii, 177. 



I Journ. f iir Pract. Cliemie, bti, 41, and Annalen der Chemie und Pharmacic, 

 xcvi, 218. 



§ The en^nlojment of the double nitrite of cobalt and jpotash as a means of sep- 

 arating cobalt from other metals was first suggested by Fischer, and afterward by 

 St Evre and Stromeyer. Aa the salt is insoluble in a solution of acetate of potash 

 and in alcohol, it is easy to wash it completely, but after washing it is difficult to 

 estimate the cobalt accurately by drying ancl weighing upon a filter. We have 

 found that a yery satisfactory result mav be obtained bv weiffhinar the cobalt in the 



t 



i 



