TRANSACTIONS OF THE SECTIONS. 47 



one G58th part of the sun's semidianieter. In order to produce a tension capable of 

 overcoming this gigantic pressure, the ditierence in temperature between the enclosed 

 hydrogen and that existing iu the solar atmosphere must be 74,910° C! In a 

 similar way ZoUner calculates the approximate absolute temperature of the sun's 

 atmosphere, which he finds to be 27,700° C, a temperature about eight times as 

 high as that given by Bunsen for the oxyhydrogen name, and one at which iron 

 must exist in a permanently gaseous form. 



Passing on to more purely chemical subjects, we find this year signalized by the 

 redetermination of a most important series of chemical constants (that of the 

 heat of chemical combination) by Julius Thomsen, of Copenhagen. This con- 

 scientious experimentalist asserts that the measurements of the heat evolved by 

 neutralizing acids and bases hitherto considered most correct, viz. those made with 

 a mercury calorimeter by Favre and Silbermann, differ from the truth by 1 2 per 

 cent., whilst the determination by these experimenters of the heat of solution of 

 salts is frequently 50 per cent, wi'ong. 



As the result of his numerous experiments, Thomsen concludes that, when a 

 molecule of acid is neutralized by caustic alkali, the heat evolved increases nearly 

 proportionally to_ the quantity of alkali added, until this reaches 1, -}, }, or ^ of a 

 molecule of alkali, accordingly^ as the acid is mono-, bi-, tri-, or tetrabasic. Excep- 

 tions to the law are exhibited by silicic, and also partly by boracic, orthophosphonc, 

 and arsenic acids. In the two latter the heat of combination is proportional for 

 the first two atoms of replaceable hydrogen, but much less for the third atom. A 

 second unexpected conclusion which Thomsen draws from his calorific determina- 

 tions is that sulphuretted hydrogen is a monobasic acid, and that its rational 

 formula is therefore H (S H). 



Another important addition made to chemistry since our last Meeting is a new, 

 very powerful, and very simple form of galvanic battery discovered, though not 

 yet described, by Bimsen. In this second Bunsen's battery only one liquid, a 

 mixture of sulphuric and chromic acids, is employed. The plates of zinc and 

 carbon can all be lowered at once into the liquid aiad raised again at will. The 

 electromotive force of this battery is to that of Grove's (the most powerful of Icnown 

 forms) as 25 to 18 ; it evolves no fumes in working, and can be used for a very 

 considerable length of time without serious diminution of the strength of the 

 current ; so that Bunsen wi'ites me that no one who has once used the new battery 

 will ever think of again employing the old forms. I had hoped to be able to 

 exhibit to the Section this important improvement in our means of producing a 

 strong cm-rent ; but war has demanded the use of other batterie.s, and Bunsen haa 

 been unable to send me a set of his new cells. 



Amongst the marked points of interest and progi'ess in Inorganic chemistry 

 during the past year we have to notice the preparation of a missing link amongst 

 the oxysulphur acids by Schutzenberger. It is the lowest known, and may be 

 called hydrosulphurous acid, H, SOj. The sodium salt, Na H SO,, is obtained by 

 the action of zinc on the bisulphite ; as might be expected, it possesses very powerful 

 reducing properties, and bleaches indigo rapidly. 



The metallic vanadates have also been carefully examined, and the existence 

 of three distinct series of salts proved, corresponding to the phosphates, viz. the 

 ortho- or tribasic vanadates, the pyro- or tetrabasic vanadates, and the meta- or 

 monobasic vanadates. Of these the ortho-salts are most stable at a high tempera- 

 ture, and at the ordinary atmospheric temperature the meta-salts are most stable, 

 whilst, as is well known, in the phosphorus series the order of stability is the 

 reverse. Thus the points of analogy and of difference between phosphorus and 

 vanadium become gi-adually apparent. 



As an illustration of the results of modern Organic research (for in viewing 

 the year's progress in this ever widening branch of chemistry it is impossible to 

 do more than give a few illustrations), I may quote Baeyer's remarkable investiga- 

 tions on mellitic acid. Originally discovered byKlaproth in Honeystone or Mellite 

 (a substance which yet remains the only source of the acid), mellitic was supposed 

 to be a 4-carbon acid. Baeyer has quite recently shown that the acid contains 

 frn^elve atoms of carbon, or has a molecular weight three times as great as was 

 originally supposed. He haa shown that mellitic acid is benzol hexacarbonic 



