CHEMISTRY. 



91 



to Hermann, that Marignac must have had 

 nearly pure ilmenium. This is stated to he a 

 necessary result from the method of prepara- 

 tion. After crystallizing out the tantalum- 

 potassium fluoride, Marignac evaporated and 

 recrystallized, obtaining a nearly pure ilme- 

 nium-potassium fluoride, from which he pre- 

 pared his metal. Hermann's paper concludes 

 with an account of his methods of separating 

 the metals of this group, and descriptions of 

 their compounds. 



Sensitiveness of Silver Salts. In continua- 

 tion of his researches on the sensitiveness of 

 silver salts (American Journal of Science and 

 Arts, No. Ixxvii.), M. Carey Lea recognizes three 

 modes in which salts of silver may exhibit their 

 sensitiveness to light, viz. : they may exhibit a 

 visible darkening ; or they may receive a latent 

 image, and this may have a capacity of being 

 rendered visible either by receiving a deposit 

 of metallic silver, or by decomposition by alka- 

 lies in connection with reducing agents. In 

 the former of these two last-mentioned modes, 

 the image is produced entirely by the addition 

 of silver not previously present ; in the latter, 

 no silver whatever is added, but that portion 

 of substance which received the direct action 

 of light undergoes decomposition by subse- 

 quent treatment. In both cases molecular 

 change is set up by the action of light: the 

 portions acted upon by light become, in the one 

 case, more apt to attract a precipitate in the 

 act of formation ; in the other case they are 

 more readily attacked by certain reducing 

 agents. Now, while the silver compounds 

 which exhibit the greatest tendency to form 

 latent images by the action of light are the 

 iodide, bromide, and chloride, Mr. Carey Lea 

 finds that the same tendency is shared, though to 

 a less degree, by other compounds, and that the 

 latent images formed upon them may belong to 

 either of the above-mentioned classes. In 

 making his experiments, the author selected 

 soluble salts of acids capable of forming insol- 

 uble or nearly insoluble salts with silver, and 

 with them he impregnated the surface of very 

 pure paper. After drying, the papers were 

 floated on a solution of silver nitrate contain- 

 ing about 20 grains to the ounce, acidulated 

 with half a drop of nitric acid (specific gravity 

 1.28), to the ounce of solution. The excess of 

 silver nitrate having been worked out, one set 

 of papers were then simply dried, and another 

 set were soaked about a minute in a 10-grain 

 solution of gallo-tanic acid, and then washed 

 again. The salts thus formed on the paper were 

 exposed to a strong diffuse light, some for 7, 

 some for 12 seconds. They were next sub- 

 mitted to the action of a very weak solution 

 of pyrogallol, ammonium carbonate, and potas- 

 sium bromide, the latter being used to check 

 the rapidity of the action of the other agents. 

 The results were as follows : 



Silver citrate and tartrate both gave rather weak 

 images. The citrate showed a strong tendency to 

 irregular reduction. Nothing of this appeared in 

 the case of the tartrate. 



Silver platinocyanide gave quite a strong image 

 stronger than any other substance tried, except, ot' 

 course, the silver bromide used for comparison. 



Silver mucate gave a very faint image with much 

 irregular reduction. 



Silver pyrophosphate behaved in the same way. 



Silver arsenite gave a moderately strong image, 

 coming next to the platinooyanide, and, like it, clear 

 and free from all irregular reduction. 



Silver sulphocyanide, an extremely faint image 

 with much irregular reduction. 



Silver antimonio-tartrate, a weak image entirely 

 free from irregular action. 



Silver fulminurate, weaker than the last mentioned, 

 hut also clear. 



Silver nitrate, similar to the last. 



Silver hippurate, an excessively faint image with 

 much irregular reduction. 



The following substances showed (with the 

 above-mentioned exposures) no trace of a la- 

 tent image : 



Silver salicylate, 

 valerate, 

 succinate, 

 sulphite, 

 res mate, 

 phosphate, 

 metaphosphate, 



Silver tungstate, 



ferrocyanide, 



nitroprusside, 



chromate, 



carbonate, 



oxalate. 



As respects the action of tannin, which was 

 separately investigated with every one of the 

 above salts, it appeared that no substance in- 

 sensitive in the absence of tannin acquired 

 sensitiveness by its presence. It was also 

 doubtful if in any case tannin increased the 

 sensitiveness of any of these substances a 

 fact which, in view of the increased sensitive- 

 ness conferred by tannin on the silver haloids, 

 is remarkable. 



New Acids. A new acid of phosphorus and 

 oxygen, standing between phosphorous and 

 phosphoric acid, has been discovered by Th. 

 Salzer, of Worms. According to the old nota- 

 tion, this acid, which has been named hypo- 

 phosphoric acid, consists of 1 atom of phos- 

 phorus and 4 atoms of oxygen. It forms a 

 rather insoluble salt. Salzer finds that the 

 acide phosphatique of Pelletier is a mixture 

 of phosphorous and hypophosphoric acids. 



C. Stahlschmidt has discovered a new or- 

 ganic acid, polyporic, occurring in certain 

 fungi of the family polyporus, which grow on 

 the stems of diseased or dead oaks. The em- 

 pirical formula is CoHjOa. This acid has a yel- 

 low color, and is so completely insoluble in 

 water that the slightest trace of a soluble poly- 

 porate in water renders the liquid turbid on 

 the addition of salt or of sulphuric acid. In 

 virtue of this property the soluble polypo- 

 rates may act as indicators in alkalimetry, 

 the turbidity serving instead of the usual change 

 of color. With all bases it forms well-defined 

 salts, of which the soluble ones, those of the al- 

 kalies, form deep-purple solutions. On heat- 

 ing polyporate of potassium to redness in a 

 combustion-tube along with zinc-powder, ben- 

 zol was obtained, which was identified by 

 its conversion into nitro-benzol. 



In a paper on the " Chemistry of Cocoa But- 

 ter," Mr. C. T. Kingzett described two new 



