238 



NA TORE 



[January 5, 1893 



In the poUerior region of the thorax the central and lateral 

 cavities are similar to those of the anterior region, whilst dorsal 

 to them the pericardial chamber lies. This chamber is separated 

 from the central body cavity by the pericardial septum. The 

 genital organs are situated immediately below the front end of 

 this septum. 



A comparison with the body cavity of Peripatus suggests the 

 following relations. In the anterior region of the thorax of 

 Pahnnonetes the dorsal sac is homologous with the dorsal por- 

 tions of the mesoblastic somites of Peripatus, and its cavity is a 

 true ctelom. The central and lateral cavities, together with 

 the cavities of the legs, represent the pseudocode. In the 

 posterior region of the thorax the cavities are all pseudoccelomic, 

 and a^ree with those of the adult Peripatus. 



December 15. — " Preliminary Note on the Relation of the 

 Ungual Corium to the Periosteum of the Ungual Phalanx." By 

 F. A. Dixey, M.A., M.D., Fellow of Wadham College, Oxford. 

 Communicated by E. A. Schiifer, P'.R.S, 



Chemical Society, December i. — Prof. A. Crum Brown, 

 President, in the chair. — The following papers were read : — 

 The isolation of two predicted hydrates of nitric acid, by S. U. 

 Pickering. The author announces the isolation of two crystalline 

 hydrates ofnitric acid: the monohydrate and the trihydrate, melt- 

 ing at - 36'8° and - i8'2° degrees respectively. In the case of 

 either the melting-point is lowered by the addition of acid or 

 water. The existence of these compounds was foreseen from 

 an examination of the curves plotted from Bertholet andThom- 

 sen's heat of dissolution values. This result is an important 

 confirmation of the author's views. — Anhydrous oxalic acid, by 

 W. W. Fisher, The best method of obtaining crystallized 

 anhydrous oxalic acid is by allowing the hydrated acid to remain 

 in contact with concentrated sulphuric acid for some months in 

 a sealed glass tube. Oxalic acid is soluble in about 30 parts 

 of cold sulphuric acid ; the anhydrous acid dissolves with ab- 

 sorption of heat, whilst the reverse is the case with the hydrated 

 acid. Anhydrous oxalic acid may be crystallized from nitric 

 acid of sp. gr. i'5. Oxalic acid may be completely dehydrated 

 in a vacuum at 60° ; the anhydrous acid is soluble in ethyl 

 oxalate or glacial acetic acid, and separates from these solvents 

 in a powdery form. — The production of orcinol and other con- 

 densation products from dehydracetic "acid," by N. Collie 

 and W. S. Myers. The authors have obtained orcinol by the 

 action of barium hydrate on dehydracetic "acid" or di- 

 methylpyrone ; on boiling a mixture of syrupy caustic soda and 

 dehydracetic "acid," a true carboxylic acid is first produced, 

 and, losing carbonic anhydride, yields orcinol. Among the 

 products of the interaction of barium hydrate and diacetylacetone 

 bright yellow needles melting at i8o-i8i° are found ; these 

 probably consist of a naphthalene derivative Ci iHx403. Amido- 

 dehydracetic "acid," obtained in long needles melting at 192- 

 196°, by the action of strong ammonium hydrate on dehydracetic 

 "acid," readily yields- dehydracetic "acid," on acid or alkaline 

 hydrolysis. — Ob-^ervations on the origin of colour and on fluor- 

 escence, by W. N. Hartley. It cannot be stated in general terms 

 that colour is due to special methods of atomic arrangement ; the 

 statement may, however, be applied in a restricted sense to 

 certain organic compounds, especially to those included in the 

 class to which organic dye-stuffs belong. It is pointed out that 

 all open chain hydrocarbons exert a continuous absorption, the 

 extent of which depends on the number of carbon atoms in the 

 molecule. The condition of strain and instability existing in 

 many coloured substances has been remarked by Armstrong ; 

 the author points out that all organic colouring matters are 

 endothermic compounds, and considers this to be the physical 

 cause of what Armstrong terms ' ' reactivity " or " high potential. " 

 It is shown that anthracene is not colourless, but has a true 

 greenish-yellow colour in addition to its fluorescence. A num- 

 ber of experiments on fluorescence are detailed, and the follow- 

 ing conclusions drawn from them :— (i) Alcoholic solutions of 

 quinine exhibit a beautiful, bright violet fluorescence. (2) 

 Hydrochloric acid is not fluorescent. (3 and 4) Quinine hydro- 

 chloride and chloroform are feebly fluorescent, but without 

 distinct colour. (5) Both hydrochloric acid and chloroform can 

 extinguish those rays which are the cause of fluorescence in 

 quinine. (6) Some alkaloids may be recognized by the degree 

 and colour of their fluorescence. (7) Normal alcohols of the 

 ethylic series and the fatty acids are fluorescent. (8) Glycerol 

 has a violet fluorescence. (9) Benzene (has a pale blue fluor- 

 escence, azobenzene a greenish-blue. (10) Rock (crystal has a 



NO. I 2 10, VOL. 47] 



pale bluish-violet fluorescence, flint glass a strong blue, and crown 

 glass a very brilliant blue fluorescence. (li) SubstHnces which 

 are not fluorescent in strong solutions may become soon dilution, 

 particularly if they exert a very powerful absorption of the ultra- 

 violet or invisible spectrum. — The origin of colour, v. coloured 

 hydrocarbons and fluorescence : a re[)ly to Prof. Hartley's 

 observations on the origin of colour and of fluorescence, by H. 

 E. Armstrong. If attention be paid to vi-ibly-coloured organic 

 substances, it is a most remarkable fact that in those cases in 

 which the "constitution" is fairly well established coloured 

 substances are found to be all of one type. The author starts 

 from this basis to inquire whether all coloured organic sub- 

 stances are not similar in type. Hartley's remark that all 

 organic colouring matters are endothermic compounds has little 

 importance in the present connection, inasmuch as the converse 

 does not hold. The author contends that before admitting the 

 fluorescence of many substances, e.g. alcohol and its homologues, 

 every precaution must be taken to ensure their purily ; instances 

 in which easy explanation of the fluore-cence of certain 

 substances is possible are given. Hartley's observation that 

 anthracene is coloured strongly confirms the author's hypothesis. 

 Anthracene is fluorescent, and may be represented by a quinonoid 

 formula, whilst its isomeride phenanthrene, which cannot be so 

 represented, is colourless and non-fluorescent. Fuithermore, 

 whilst intense colour is produced by "weighting" what the 

 author terms the "quinonoid radicles" of anthracene by re- 

 placing the central hydrogen atoms by a halogen, no such effect 

 attends the similar treatment of phenanthrene, dibromophenan- 

 threne being colourless like the hydrocarbon. And yet anthra- 

 quinone and phenanthraquinone are coloured yellow and deep 

 orange respectively. Reference is made to other coloured 

 hydrocarbons, viz. carotin and the red hydrocarbon, CggHig, 

 recently investigated by Graebe. The formula assigned to the 

 latter by Graebe — 



CeH/ \H4C6 



— is an improbable one ; such a substance would be colourless. 

 The author gives a possible constitution, and, for the present, 

 proposes to call the compound "erythrophene." The yellow 

 hydrocarbon, C._;gH]g, obtained together with this, is possibly a 

 diphenylaied anthracene, and may be termed " xanlhophene." 

 The "quinonoid radicles" in both hydrocarbons are heavily 

 "weighted," hence their strong colour. With reference to 

 Hartley's statement that a very little shifting of the region of 

 absorption determines the presence or absence of colour in a 

 compound, it is contended that this shifting mny be due to a 

 special character of structure. The author then explains his 

 views as to the manner in which the "quinonoid mechanism" 

 conditions colour. He suggests that in quinonoid compounds 

 there are two "colour cent es" currespomiing to and expressed 

 by the symbol 3 in formulae such as he has used in representing 

 coloured substances. These centres co-operate in producing 

 colour through interaction of the light waves which traverse 

 them. Substances in which there are no such co-operating 

 centres may absorb generally and selectively in "ultra" or 

 "infra" regions of the spectrum, but without exhibiting "visible 

 colour." — The origin of colour, vi. azobenzene, by H. E. 

 Armstrong. Azobenzene, a highly-coloured substance, is 

 generally represented as Ph.N : N.Ph, a formula in disaccord 

 with the author's hypothesis explained in the preceding paper. 

 Moreover, the formulae usually attributed to the colourless diazo- 

 salts (Ph.N : N.Cl, for example) represent them as comparable 

 in constitution with azobenzene. The behaviour of azobenzene 

 towards bromine and other reagents leads the author to doubt 

 the correctness of the conventional formula assigned to it, and 

 to consider the following a more probable one : — 





■N 



"\^ 



— The reduction products of dimethyldiacetylpentane, by F. S. 

 Kipping. The author shows that dimethyldiacetylpentane, a 

 diketone produced by the hydrolysis of ethyl dimethyldiacetyl- 

 pimelate is converted by reduction with sodium in a moist 

 ethereal solution into dipielhyldihydroxynonane and a compound 



