270 



NA TURE 



\yan. 31, 1878 



relation R'^O : M^g^s = 3" : 100. or nearly 3 : i, thus 

 giving the simple formula R"3M''208 ; this latter the 

 author considers the more probable. Whatever formula, 

 however, may be taken for the mineral it differs from 

 niobates hitherto described, the one view making it an 

 approach to a simple pyroniobate, the other making it an 

 orthcsalt like Fergusonite, but partially acid in character, 

 or containing basic hydrogen. 



Molybdenum. — The atomic weight of this metal has 

 hitherto been quite uncertain, some chemists regarding it 

 as 96, others as 92. Fresenius, the leading authority in 

 analytical chemistry, has always adopted the latter num- 

 ber. Prof. Rammelsberg, of Berlin, has lately settled the 

 question by careful experiments on the reduction of mo- 

 lybdic acid in an atmosphere of hydrogen, and has 

 found 96 to be the correct atomic weight, - 9618 

 being the exact number obtained. Taking this number 

 as a basis, he has sought to solve the problem of the 

 composition of the yellow phospho-molybdate of ammo- 

 nium, which is used generally for the determination of 

 phosphoric acid, and the exact formula of which has 

 never been satisfactorily determined. A large number of 

 analyses of the ammonium salt and the corresponding 

 potassium salt show that the composition is undoubtedly 

 3(NH4)20 + P2O5 -f 22M0O3 -f 12H2O. 



Relations between the Volumes of Silver 

 Salts. — H. Schroder communicates an interesting series 

 of observations on this subject in the Berichte der 

 deutschen chemischen Gesellschafi, for November, from 

 which it appears that the atomic volumes {i.e., the quo- 

 tient resulting from the division of the molecular weight 

 by the specific gravity) of these salts are all simple mul- 

 tiples of the atomic volume of silver, or rather of its half 

 atomic volume, 5 '14. In the fatty series an accession of 

 CH2 to a compound increases the atomic volume by 

 3 X 5 '14. For example : — 



C2H3Ag02=ioX5-H=5i"4 

 C3H5AgO£= 13 X 5-i4=66-8 

 C4H,Ag02=i6xs-x4 = 82-2 

 C5H9Ag02= 19x5-14=977, &c. 

 C6H5CAgO, = 2oX5-i4=i02-8 



Ornithuric Acid. — Prof. Jaffe, of Konigsberg, in the 

 course of experiments on the transformation of organic 

 bodies on passing through the digestive organs of fowls, 

 has obtained a new acid in a way decidedly different from 

 the usual methods of chemical synthesis. Benzoic acid, 

 CgHgCOOH, which has been given to birds, is found to be 

 entirely changed by passing through their organisms into 

 a new and well-defined acid, which crystallises in colour- 

 less needles, forms a series of salts, and receives the name 

 ornithuric acid. It appears to arise from the combination 

 of benzoic acid with a base C5H12 N2O2, present in the 

 system, and which can be separated from ornithuric 

 acid by treatment with hydrochloric acid. The formation 

 is as follows : — 



2C6H5COOH-{-C5Hi2N202=Ci9H2oN204+2H20. 



Distillation of Organic Liquids by Means of 

 Steam. — Prof. Naumann, of Giessen, describes, in a 

 recent series of papers in the Berichte der dent. chem. 

 Cesellscha/t, the results of his observations on the pheno- 

 mena attendant on the passage of steam through organic 

 liquids. As is well known to the experimental chemist, 

 aqueous vapours, on passing through a liquid, carry with 

 them frequently large portions of the latter, even when it 

 boils at a temperature far above that of water — aniline, 

 for example, at 180°. The process also is one of every- day 

 occurrence in the organic laboratory, being used for the 

 purpose of separating such liquids from their impurities. 

 Prof. Naumann has studied in this connection liquids both 

 specifically Ughter and heavier than water, as well as liquids 

 boiling below and boiling above 100° C., recording the 



physical phenomena produced by the passage through each 

 of a regular current of steam. In all cases he finds them 

 obeying a few invariable laws, viz., 1°. For every mixture 

 of a liquid with water there is a constant boiling-point, 

 which is below that of the lower boiling liquid "2°. A 

 constant ratio exists between the respective quantities of 

 the two liquids found in the distillate "3°. The tempera- 

 ture of the distilling vapours is always slightly higher 

 than that of the mass of liquid. From among the 

 numerous results the following will convey a general idea 

 of the experiments. The first column contains the 

 boiling points of the respective liquids, the second the 

 temperature of the liquid while steam is being passed 

 through it, and the last the number of cubic centi- 

 metres of the liquid found in the distillate for every 

 100 c.c. of water : — 



Benzene 

 Toluene 

 Xylene ... 

 Nitrobenzene 



. 79-5 ... 66-5 ... 8-S 



. 108-5 ... 82-4 ... 21-2 



. 1355 ... 89 ... 44 

 . 205 ... 98-5 ... 14 



An attempt was made to discover a connection between 

 the molecular weights of the three first hydrocarbons of 

 the aromatic series and the respective quantities of these 

 liquids in the distillates, but without success. While 

 studying the relations of the numbers yielded by the 

 experiments, Prof. Naumann finally discovered that all 

 the liquids obeyed a general fixed law, viz., ivheit a liquid 

 is distilled by means of steam, the ratio between the 

 vohimes of the liquids and the water in the distillate, 

 expressed in multiples of their molecular weights, is equal 

 to the ratio between their vapour-tensions at the tempera- 

 ture at which the distillation occurs. It is at once evident 

 that by the discovery of this law the chemist is placed in 

 command of a most valuable auxiliary for determining 

 the constitution of a variety of compounds at present 

 to a certain extent doubtfiiJ. The law holds equally good 

 for any liquid the vapour of which is used instead of that 

 of water. 



GEOGRAPHICAL NOTES 



Early African Explorer. — Don Marcos Ximenez 

 de la Espada of Madrid is now having printed a docu- 

 ment of extraordinary interest for geographical science, 

 viz., an account of the travels of an unknown missionary, 

 of the fourteenth century, which Don Marcos has re- 

 cently discovered. The enterprising author, in the years 

 from 1320 to 1330, undertook extensive travels in Africa, 

 not only along the west coast to Sierra Leone and thence 

 to Dahomey, but also, it is stated, from the mouth of the 

 Senegal river straight across the interior of the great 

 continent. He visited the Soudan States, got as far as 

 Dongola, and thence proceeded down the River Nile, 

 finally reaching Damietta. 



African Exploration. — In reply to a question 

 from Mr. H. Samuelson last Friday in the House of 

 Commons, the Chancellor of the Exchequer stated that 

 it was not the intention of Government at present to 

 devote any public money to African exploration. We 

 can hardly expect that they would in the present state of 

 public affairs ; and even if they could it would be diffi- 

 cult to see in what direction they could take action. 

 There are many expeditions of various kinds in the 

 African field at present, working away with little or no 

 connection with each other ; even the International 

 African Association has not been able to organise them, 

 but is simply sending out more expeditions. There 

 seems to us to be considerable waste of power and 

 resources here. 



Mr. Stanley. — The Geographical Society's dinner to 

 Mr. Stanley is to take place on February 9. Arrange- 

 ments are being made to accommodate the Fellows and 



