442 



NATURE 



\_Sept. 20, 1877 



the points of first and last appearance of some 13,000 

 meteors observed by Heis and the various colleagues who 

 assisted him from time to time, followed by partial dis- 

 cussion of the results and catalogues of radiant points. 

 A fuller account of this valuable publication must be 

 reserved for a future note. The first number of this 

 series contains Heis's long-continued observations on the 

 zodiacal light. 



A New Comet.— M. Coggia, of the Observatory at 

 Marseilles, discovered a faint comet on September 14. 

 Its position at I4h. 38m. 8s. mean time at Marseilles, 

 was in R.A. 8h. 32m. 3'is. ; N.P.D., 41° 45' 59." Daily 

 motion in R.A. — 45 seconds, in N.P.D. -|- 18 minutes. 

 The comet has a central condensation, with trace of a tail. 



CHEMICAL NOTES 



Action of Organic Substances increasing the 

 Sensitiveness of certain Silver Salts.— Mr. M. C. 

 Lea, of Philadelphia, has criticised, in a short paper, the 

 theory brought forward by Poitevin and Vogel, that 

 increased sensitiveness was imparted to the halogen com- 

 pounds of silver by certain organic substances in virtue 

 of their affinity for hydrogen. From experiments he has 

 made he is led to the conclusion that these organic sub- 

 stances do not form substitution products as might be 

 expected if they possessed an affinity for hydrogen, but 

 that they all act as reducing agents. The natural view, 

 therefore, of their action which Lea deduces is that the 

 affinity of the organic substance for oxygen assists that of 

 halogen for hydrogen, and, under the influence of light, a 

 molecule of water becomes decomposed. That, in the 

 case of tannin and silver iodide for instance, the tannin is 

 oxidised, the iodine converted into hydriodic acid, and the 

 silver salt more or less reduced. According to this theory 

 traces of free acid would be found instead of the iodine 

 substitution product. His experiments have confirmed 

 this supposition, and he concludes, therefore, that the 

 increase of sensitiveness produced by organic substances 

 takes place in virtue of their affinity for oxygen promoting 

 the decomposition of water by the halogen employed. 



Heat of Combustion of Oxygen and Hydrogen 

 IN Closed Vessels.— In a recent number of the Journal 

 of the German Chemical Society there are some experi- 

 ments on the above subject communicated by Than. 

 He has modified Bunsen's ice calorimeter, so as to make it 

 available for heat determinations in chemical action, and 

 by this means he has obtained accurate results of the 

 heat of combustion of electrolytic gases in closed vessels. 

 The terms " heat of combustion," or " total difference of 

 energy," are used by Than to express the quantity of 

 actual energy evolved when the combining gas, in the case 

 of oxygen and hydrogen at 0° and 760 mm., is completely 

 converted in a closed vessel into water. Taking the 

 atom of hydrogen as unity he finds that a gramme of 

 hydrogen uniting with the requisite quantity of oxygen in 

 a closed vessel to form water, produces 33982 units of 

 heat, which number agrees closely with that found by 

 Andrews, viz , 33,970. 



On Vapour Volumes in Relation to Avogadro's 

 Law.— In the same journal {Ber. chem. Ges., x.) there is a 

 paper by Troost, detailing experiments made to determine 

 the accuracy of Avogadro's theory that " equal volumes 

 of substances in the state of vapour contained the same 

 number of molecules," i.e., that the volume of the mole- 

 cule of hydrogen being called 2, the volume of all other 

 molecules must also be 2 ; instead of as happens in cer- 

 tain cases, apparently 4, 6, or 8. The method of experi- 

 ment adopted was to introduce into the vapour of chloral 

 hjdrate a salt containing water having a dissociation- 

 tension nearly equal to that of chloral hydrate ; if the 

 chloral hydrate vapour undergoes dissociation, and con- 

 sists of equal volumes oi chloral and aqueous vapours, 

 then the vapour volume will remain constant ; but if 

 chloral hydrate is volatile as such, its vapour will be free 



from water, and on introducing the salt it will give up 

 water, and the volume of vapour will increase till the 

 dissociation-tension is reached. The salt used was potas- 

 sium oxalate, containing one molecule of water. Troost 

 has found that the volume increases on the addition of 

 the oxalate, leading him therefore to the conclusion 

 that chloral hydrate undergoes volatilisation without 

 decomposition. 



Chemical Constitution of the Minerals 

 Hatchetolite and Samarskite, from North 

 Carolina.— Mr. O. D. Allen has lately had an oppor- 

 tunity of making some further experiments on the above 

 minerals lately described by Mr. J. L. Smith, and of which 

 a short note was given some time ago in NATURE. His 

 analytical results confirm those of Mr. Smith, and from 

 these he deduces a ratio among the elements closely 



corresponding to that of R2R32H2O, or 



R2R2O7 + 2R R2O4 + 4H2O, 



when R represents one atom of a bivalent radical, or two 



of sodium, and R, tantalum or columbium. The investi- 

 gations of Rammelsberg point to the conclusion that 

 three columbates (having columbium replaced by tantalum) 



occur in minerals, viz., RCb206, RjCbjO,, and RjCbjOg, 

 which, singly or combined with each other, constitute 

 mineral species. Mr. Allen regards hatchetolite as com- 

 posed of the first two, with a small quantity of normal 

 titanate. He also thinks that it may have resulted from 

 the alteration of a mineral possessing essentially the 

 same composition aspyrochlore,by hydration, and removal 

 of alkaline fluorides. From his analysis of samarskite a 

 ratio is obtained closely approximating to that required 



by the formula RoRjO, + RjRjOg. From this it would 

 appear that samarskite closely resembles fergusonite in 

 chemical constitution, the formula of that latter body, 

 deduced by Rammelsberg, being R3(Cb, Ta)20j,. 



On A New Class of Bodies termed Platoiod- 

 NITRITES. — Nilson has lately described in the Ber. Berl. 

 chem. Ges. x., a series of bodies to which he has assigned 

 the above name, and which he prepares by acting on 

 potassium or barium platinonitrite with an alcoholic solu- 

 tion of iodine. Aldehyde is evolved on heating the 

 mixture, which latter, originally brown, becomes of an 

 amber colour. The platoiodnitrite is deposited in crys- 

 tals. He has prepared the potassium salt in four-sided 

 amber prisms, and assigns to it the formula K^NjO^UPt 

 (H20)2. He represents the reaction by the following 

 equation : — 



K2(N02)4Pt -f I2 + (C2H60)3= K2N204l2Pt -f CjH^O + 



lC2H50i\0),-|-2tH20). 

 He describes also a new acid obtained by decomposing 

 barium platinonitrite with sulphuric acid and evaporating 

 in vacuo. The first product consisted of an acid corre- 

 sponding to the platotetranitrosylic acid of Lang, but on 

 evaporating the solution to dryness, after removal of the 

 first crystals, a permanent residue of a brownish-green 

 colour remained, which, after drying over sulphuric acid, 

 gave on analysis the following composition : H4(N02)3 

 Pt30 . 2(H20). The author calls this triplato-octinurosylic 

 acid. 



A New Acid.— At the last meeting of the Nieder- 

 rheinische Gesellschaft fiir Natur und Heilkunde of Bonn 

 Prof. Mohr announced the discovery of a new acid of 

 phosphorus and oxygen, by Herr Th. Salzer, of Worms. 

 The new acid stands between phosphorous acid and 

 phosphoric acid, and consists, according to old notation, 

 of one atom of phosphorus and four atoms of oxygen. It 

 has been named hypophosphoric acid. It forms a rather 

 insoluble soda salt. Herr Salzer found that the " acide 

 phosphalique " described by Pelletier consists of a mixture 

 of phosphorous and hypophosphoric acids. 



