E. 0. Ilovey — Cherts of Missouri. 401 



The solution itself is opaque by reason of its intense color. 

 "When largely diluted it is yellowish brown and perfectly trans- 

 parent. 



From the method of obtaining this substance there seem to 

 be only two possible explanations of its nature. First, that it 

 is metallic platinum in a state of solution ; this is decisively 

 negatived by the reactions just described. Second, that it is a 

 chloride containing less chlorine than platinous chloride ; there- 

 fore a sub-chloride. If the precipitate obtained by potash could 

 after washing be dissolved in hydrochloric acid its constitution 

 could easily be determined. But during the washing it seems 

 to be converted into metallic platinum. 



I have noticed that when a solution of the ruby red salt 

 2KC1, PtCl 3 is spread on paper and exposed to sunlight it does 

 not blacken but assumes a yellowish brown color ; it would 

 seem therefore that light acts upon it much in the same way 

 as a hypophosphite, reducing it probably to a sub-chloride. If 

 the reduction was to metallic platinum this would be shown 

 by the production of an intense blackness. 



In all this, analogy with silver salts is unmistakable. .Pure 

 silver chloride is not reduced to metal by the action of light, 

 for after exposure it yields nothing to nitric acid. Both metals 

 seem to form sub-chlorides, the oxids corresponding to which 

 are very unstable. 



Art. LYII. — A Study of the Cherts of Missouri;* by 

 Edmund Otis Hovey. 



The investigations herein reported were carried forward on 

 material collected by the officers of the State Geological Sur- 

 vey of Missouri and kindly furnished me by Mr. Arthur 

 Winslow, when State Geologist, together with a long list of 

 references to the literature on the subjects of flint and chert. 

 The chemical analyses which will be quoted were made, unless 

 otherwise stated, at the office of the survey, by Mr. J. D. 

 Robertson. Thirty-eight specimens from different parts of the 

 State, and fifty thin sections made from them, were examined. 



The material falls naturally into two groups according to 

 geological age. About half of the specimens came from the 

 Lower Magnesian Seriesr (Cambrian?), and the rest from the 



* Read before the Geol. Soc. Am., August, 1894. 



f The Missouri strata which have long gone by the name of the " Magnesian 

 Limestone Series " have been designated the " Ozark Series " by Prof. G. C. 

 Broadhead (Amer. Geol.. vol. viii, 33, 1891) aDd the term has been adopted by 

 the Missouri Geological Survey. 



