ON THE HYDROLYSIS OF SUGARS. 277 



levulose p<art of the cane sugar; the compound of sugar and acid (for 

 no obvious reason) then at once parts with glucose, leaving the chlor- 

 hydrin of levulose behind. This latter gives levulose or a disaccharide, 

 according to circumstances. 



moi Donath, supposing from his experiments at 120° that glycerol 



■ inverts sugar, put forward the theory that the glycerol exists as 

 a hydrate, the nascent free water molecules from which are the active 

 agent in hydrolysis. 

 1SQ1 Bordt, however, has shown that Donath 's experimental work 



was unsound and that glycerol really retards inversion instead of 

 promoting it. 



^q(\■^ Rohland, in a theoretical paper, put forward the view that nas- 



' cent molecules of water formed from H and OH ions bring about 

 the inversion. Any cause, sucli as the presence of an acid, which increases 

 the number of nascent water molecules formed in unit time, will also 

 accelerate inversion. 

 1 Qn9 Noyes and Samnet, on the other liand, suggested in a footnote 



to a lecture on catalysis that the hydrogen ions are hydrated and 

 1 qno *'^^^ their water is more active than ordinary water molecules. The 



ions thus act merely as water carriers. Rohland claimed that this 

 was his theory but the two are not by any means the same. 

 1 ort . Mellor and Bradshaw have discussed inversion mathematically 



with regard to the secondary changes which occui', with reference 

 especially to the bi-rotation of glucose and levulose. There is, how- 

 ever, no experimental evidence of such secondary actions occurring after 

 inversion. 



E 4. — The Additio7i Theory of Sugar Inversion. 



1 QDI Ostwald has admitted that ' there is nothing in the laws of 



chemical kinetics to disprove the addition theory (of chemical 

 change) but it must be proved that the partial actions proceed more 

 rapidly than the main action.' 



It will be seen that Wohl's theory is essentially an addition theory of 

 inversion. If from other considerations it appears highly probable that 

 the addition theory is the correct explanation, the fact that a ' mono- 

 molecular ' law is followed ought to be taken as a sufficient indication of 

 the correctness of the assumption mentioned by Ostwa' 1 



The addition theory has been developed systematically by Dr. E. F. 

 •inn A Armstrong and the author in a comparative study of the action 

 of acids and enzymes on various sugars. The theory put forward 

 was that the sugar enters into some kind of combination with the acid 

 and some water molecules. An ' active system ' thus arises which fulfils 

 all the requirements of Arrhenius's ' active sugar ' and which breaks down 

 into invert sugar and hydrated acid according to a mono-molecular mass 

 action. 



As only a small proportion of the acid molecules are engaged at any 

 moment, the acid is usually in large excess. If, however, very small 

 quantities of acid are used, the sugar is in excess, so that during the first 

 part of the hydrolysis Wilhelmy's Law is not followed but the change 

 approximates to a linear function of the time, as is frequently observed 

 in the case of enzyme action. It was further shown that the effect of 

 neutral substances, the influence of temperature and concentration, could 

 be very satisfactorily explained on this hypothesis. 



