( 558 ) 



the acid. It' tlie vclocilv of Imiist'oniuUioJi is nieasurod uiidcr these 

 circunistances it is no matter for surprise fir.sthi that no reaction 

 constant is found. si'coiiiJh/ that the reaction coefficient constantly 

 diniinislie.s as tiie inner parts of the crystals get more and more 

 inaccessil)le to the acid. As expected hefoi-eliand tiie experiment has 

 shown tliat veiT small crystals or the powdei-ed substance ai-e, on 

 account (»f tiie larger free sui-face, more rapidly trausf()rme<l than 

 the larger crystals. The ('((ntinuation of the research will show that 

 the transformation is nKUiomolcciilai- and must, therefoi-e, he taken as 

 a real disj)lacement of atoms (])erliaps of two displacements one of 

 winch takes place with very great velocity). It is a i-emarkahle fact 

 that there should take place inside the molecule of a solid sid)stance 

 a displacement of atoms, an internal change of equilihrium leaving 

 the molecule intact, l>y mere contact with sulphuric acid, without 

 there being any question of solution. 



Although we coidd not expect to get i-eaction-consiants for a 

 heterogenous mixtiii-e of a solid substance and sul|ihui-ic aci<l. this 

 should be duly the case when we woi-ked in a solvcjil. Here however 

 a difticulty occurrc(l which at lir>t threatened to put a slop lo the 

 fiirlhcM' prox'culion of the re>earch. A soKcul ^vas ^vaut•'d which 

 had no action either on tribromo|>henoll)i-omine or sulphuric acid. 

 Acetic acid scarcely di>>ol\ed the lirst substance and chloroform 

 appeared to dis.Mtlve oidy traces of JM) per cent sulphuric acid. It 

 was tinally decided to choose the lattei- .solvent ajid to thoi-ouiihly 

 shake the solution with sulphui-ic acid V. The ex])erimenl [>i'o\ed 

 that (tn ajtplying the forunda of the lirst order, constant reaction- 

 coetKicients made their appeai-ance. A first residt was thus obtained; 

 the transformation does not ]»roceed bimolecuiai'ly . 



Mr. Bkt,zf,k has now studied the iidluence of the cojicenlratioii of 

 the sulphui-ic aci<l and the tempei-ature. 



In most of the experiments, 3 grams of the substance \vere 

 dissolved in 150 cc. of pure chloroform "j, the solution >li-ouiily 

 shaken with the acid and aftei- deliiiite times 25 vv. were titrated. 



Use has been made of: 



a. H,S(), with about 367„ SO,, h. ILSO, with about i" ,, SO, 

 r. e([ual volumes of /; and d d. IM^ pei' cent Ik^SO^. 



In the following tables the results ol»taijied are not giveji in the 

 form of reaction-constants, but to make the matter moi-e plain, the 



1) A uniform emulsion is very soon obtained. 



-) The cliloioform was agitated a few times with water, diied over calcium- 

 chloiide, shaken with strong sulphuric acid and redistilled : it was preserved in 

 the dark. 



