98 R. H. A. PLIMMER. 



The only difference in the two mixtures consisted in the amount of 

 copper sulphate added to remove the hydrogen sulphide ; a slight excess 

 of this compound in the solutions could make no difference to the 

 rotatory power since its colour was scarcely apparent, nor to the reducing 

 power by Allihn's method, where an excess of copper sulphate in the 

 Fehling's solution taken is always present. 



Before preparing the osazones the solutions were again neutralised, 

 whereby the excess of copper was precipitated as hydrate and filtered off; 

 in some cases, however, a dark blue solution resulted, from which the 

 copper separated on adding the phenylhydrazine hydrochloride and 

 sodium acetate. This mixture was used in preference to the phenyl- 

 hydrazine and glacial acetic acid, since an excess of the latter might cause 

 hydrolysis of the lactose, as often happens with cane-sugar. For every 

 gramme of lactose in solution one and half times its quantity of phenyl- 

 hydrazine hydrochloride and twice its quantity of sodium acetate were 

 added ; and the mixtures were heated on the water-bath for about 

 2 hours after filtering from a small amount of resin and copper, if any. 

 The osazones never came down whilst the solutions were hot, but on 

 cooling crystals were always obtained. These were filtered off and washed 

 thoroughly with cold water. They were then washed with boiling water, 

 in which they completely dissolved leaving behind a resin, and on cooling 

 they again separated ; in this way they were recrystallised, and after 

 again filtering off and washing with cold water, they were dried at 

 110 C. and in many cases analysed. 



In order to show that this method which I have adopted is adequate 



to display the presence of lactase, if any ferment existed in the solution 



I give also protocols of experiments made with extracts of mucous 



. membrane of the small intestine, in which, as is well known, lactase is 



/certainly present. Here the osazone obtained was not completely 



soluble in boiling water ; the insoluble portion was therefore dissolved 



in dilute alcohol for recrystallisation and analysed after drying at 



110 C. 



The results are best seen from the table, in which are included the 

 figures obtained with a 2 per cent, lactose solution before and after 

 hydrolysis with acid ; 20 c.c. of the solutions were in most cases taken to 

 determine the reducing power. The additional data are given in the 

 protocols. 



