CHEMISTRY. (ATOMIC WEIGHTS.) 



117 



nary yellow phosphorus. It can not, therefore, 

 be used with that variety. Experiments with 

 phosphorus, which is capable of being raised 

 a much higher temperature, were, however, 

 successful. When dry hydrogen is led through 



glass tube containing red phosphorus, and 

 afterward through a wash bottle containing 

 water, practically pure hydrogen is found to es- 

 cape. Immediately, however, a gas flame is 

 brought under the part of the tube containing 

 the phosphorus, combination occurs, and the 

 gas issuing from the wash-bottle inflames in 

 the air. The nonspontaneously inflammable 

 gaseous hydride of phosphorus is also therefore 

 accompanied by a smaller quantity of the sponta- 

 neously inflammable liquid hydride, and both 

 substances may be obtained for demonstration. 

 The new mode of preparation is recommended 

 by the author as being more convenient than 

 the old-established method, as forming an excel- 

 lent example of the direct combination of two 

 elements, and as furnishing ample demonstra- 

 tion of all three hydrides of phosphorus, the 

 gaseous, liquid, and solid. 



For a simple and rapid method for standard- 

 izing a permanganate solution, Charlotte F. 

 Roberts recommends, first, the determination of 

 its strength by comparison with electrolytic 

 iron, and then, by immediate titration with fer- 

 ric chloride, of the exact amount of iron in each 

 cubic centimetre of the latter solution. This 

 being ascertained, the ferric-chloride solution 

 can be employed at any time for the standardi- 

 zation of potassium permanganate. 



Chlorine is conveniently generated for labora- 

 tory purposes by F. A. Gooch and D. A. Kreider 

 by the action of hot hydrochloric acid in a half- 

 strength solution upon lumps of potassium chlo- 

 rate. These are placed in the upper chamber of 

 & side-neck test tube constricted in the middle. 

 The tube is fitted with a funnel tube reaching to 

 the bottom, and immersed in a flask filled with 

 hot water. When the acid is at 81 the percent- 

 age of chlorine in the gas given off is 84. The 

 chlorine dioxide may be eliminated by passing the 

 gases through a wash bottle containing a satu- 

 rated solution of MnCl 2 in strong hydrochloric 

 acid at 90, and may be still further removed by 

 passing the gas through a hard-glass tube filled 

 with asbestus and heated. 



For a new reaction illustrating the phenome- 

 non of dissociation, Alexander Gunn dissolves 

 about 0-2 gramme of zinc sulphate in 5 cubic cen- 

 timetres of distilled water; adds ammonia drop 

 by drop, until two drops in excess of the amount 

 required to redissolve the precipitate ; then adds 

 10 or 12 drops of a 10-per-cent. solution of sodi- 

 um phosphate and 5 cubic centimetres of water. 

 The solution is perfectly bright. On applying 

 heat, the liquid becomes opaque, the turbidity in- 

 creasing as the temperature rises, till, when boil- 

 ing, a thick curdy precipitate falls. On now 

 immersing the test tube in cold water the pre- 

 cipitate will quickly disappear, leaving the solu- 

 tion as bright as it was at first. The production 

 of the precipitate by heating can be repeated 

 many times if care be taken to prevent loss of 

 ammonia. Of the two possible explanations of 

 this reaction, reasons are given showing that it 

 can not be due to the loss of ammonia by heat, 

 and other reasons for ascribing it to dissociation. 



A method of obtaining a new rhodamine, or 

 pink coloring matter, by the interaction of chlo- 

 ral hydrate and an alkyl derivative of metam- 

 midophenol, is described by Dr. Caro. A salt of 

 a leuco base is formed, which latter, on oxida- 

 tion by ferric chloride, gave a blue coloring mat- 

 ter. It was shown by experiment that on heat- 

 ing a solution of this blue compound in waler it 

 turned, by an intramolecular change, to a fine 

 pink. 



Atomic Weights. E. Vogel assumes, in a 

 communication to the Royal Academy of Bel- 

 gium, that, in spite of Stas's conclusion that the 

 atomic weights of the elements have no common 

 measure, Prout's hypothesis has recently been 

 gaining ground. The experiments of Hinrichs 

 have thrown doubt upon the atomic determi- 

 nations of Stas ; and the suppositions made by 

 Stas himself place it beyond doubt that all his 

 atomic weights are'inaccurate. The cause of the 

 great discrepancies in value found by Stas lies 

 in the variation of the weights of the substances 

 taken. When to a solution of an alkaline chlo- 

 ride is added nitrate of silver to slight excess, a 

 precipitate will be formed on adding more chlo- 

 ride. Experiment shows that a precipitate is 

 also formed on adding more nitrate, up to a cer- 

 tain limit which Mulder termed the limit of 

 silver as distinguished from the limit of salt for 

 the. addition of the chloride. The author shows 

 that the true atomic weight can not be derived 

 from the mean between these two limits, and 

 proves from Stas's own data that they may be 

 equally well interpreted for entire as well as' for 

 fractional multiples of the atomic weight of hy- 

 drogen. 



From a discussion of some of the results ob- 

 tained by J. P. Cooke, Dumas, Stas, and others, 

 M. G. Hinrichs concludes that he has reason to 

 regard the following* atomic weights Cl 35-5, 

 Br 80, I 127, and S 32 as correct, if silver be 

 taken as 108. 



In the course of an investigation concerning 

 the atomic weight of copper, Messrs. Richards 

 and Rogers, of Harvard University, have ob- 

 served that cupric oxide prepared by ignition of 

 the nitrate always contains a "considerable 

 amount of occluded gas, chiefly nitrogen ; while 

 that prepared from carbonate invariably shows 

 no signs of occluded gas. This fact is of con- 

 siderable importance, inasmuch as the previous 

 determinations of the atomic weight of copper 

 are affected by it and will be rendered more or 

 less inaccurate. The authors show, moreover, 

 that the phenomenon is also exhibited by oxides 

 of zinc, nickel, and magnesium, when prepared 

 by ignition of the nitrate. In the case of mag- 

 nesium the amount of occluded gas is extraordi- 

 narily large, exceeding a hundred cubic centi- 

 metres from 10 grammes of oxide. Hence it is 

 considered necessary that the atomic weights of 

 these metals should be subjected to revision, 

 with account taken of these facts: and until this 

 is done the values hitherto accepted can be con- 

 sidered as only approximate. 



Taking the temperatures of decomposition as 

 an index of stability, G. H. Bailey arrives at the 

 following generalizations as to the stability of 

 the typical oxides in relation to the atomic 

 weights of the elements from which they are 

 derived: 1, That in the even series the oxides 



