228 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



prism. In fig. 40 is seen a diagrammatic section of the instrument 

 full size, with wave-length scale. 



Ultramicroscopic Observations : The Characterisation of Inorganic 

 Colloids.* — W. Biltz has carried out a series of ultramicroscopic experi- 

 ments on very dilute solutions with the object of making observations 

 on inorganic matter so finely divided as to be within appreciable reach of 



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iStvivK^. - 3/l^/},^v^v&. 



molecular division. In addition to completing some earlier investiga- 

 tions he wished to show in what way an ultramicroscopic image is 

 dependent on the mode of preparation of the medium. Some of his 

 previous work f had shown that in an ultramicroscopically discontinuous 

 separation of elementary sulphur and selenium, an undoubted continu- 

 ous formation of a colloidally suspended substance had taken place. 

 This result naturally suggested further investigation. 



* Nach. von d. Koiiig. Gesell. d.Wiss. zu GottiDgen (Math.-Phvs. Klasse, 1906) 

 pp. 141-56. + Op. cit., 1904, p. 300. 



