RECENT ADVANCES IN SCIENCE 



27 



its way into the manufacture of metallic alloys, including 

 steels. Such a list covers almost the entire range of chemical 

 industry. Some of these operations are almost entirely 

 colloidal in nature ; in others the colloid state appears in at 

 least one stage. As a matter of fact industrial practice has 

 in many cases outrun the theory of the process. That in 

 itself is the best argument for a vigorous prosecution of research 

 in this subject. 



ORGANIC CHEMISTRY. By P. Haas, D.Sc, Ph.D., St. Mary's 

 Hospital Medical School, London. 



The determination of the constitution of lactose forms the 

 subject of a paper by Haworth and Leitch (/. Chem. Soc. 

 191 8, 188). Any constitutional formula for lactose must 

 account for the fact that it is a reducing sugar and gives 

 on hydrolysis one molecule of glucose and one of galactose ; 

 these two hexoses must therefore be united together in some 

 such way as to leave an active terminal group capable of exerting 

 reducing action. Evidence is now furnished to show that the 

 reducing property of lactose is attributable to the glucose 

 moiety, the reducing property of the galactose having become 

 latent by its combination with the glucose molecule. It has 

 already been shown by Ruff and Ollendorff {Berichte, 1900, 33, 

 1802) that the anhydride linking of glucose with galactose does 

 not concern the hydroxyl groups attached to the second and 

 third carbon atoms from the reducing end of the glucose chain ; 

 the fourth hydroxyl group is likewise not involved because this 

 is occupied in the 7-oxide linking of the glucose complex. The 

 galactose reducing group in its union with the glucose molecule 

 must therefore have involved either the fifth or sixth hydroxyl 

 group of the latter, as shown by the following formulae : 



CH 2 . OH 



,-CH- 



-O 



-CH 



-CH- 



-O- 



O 



o 



L 



CH.OH 

 CH.OH 



CH 



CH.OH 

 CH a . OH 



O 



-CH 3 

 CH.OH 

 -CH 

 CH.OH 



CH.OH 

 — CH . OH 



II. (Melibiose) 



One of these two formulae will represent the constitution of 



