De. W. Wallace on the Chemistry of Sv^ar Refining. 369 



sucar called sweeter than another, the specimens being equally pure, as 

 if sugar could be anything but sugar ; and it is a fact that many re- 

 finers refuse to purchase fine large-grained muscovado, and prefer 

 smaller crystals, inferior in point of purity, simply because the larger 

 crystals dissolve less rapidly in the mouth, and thus appear less sweet. 

 It appears almost incredible that such ignorance as this should exist in 

 a country where the standard of general education is so high. 



Cane sugar is devoid of odour and coloui-. It is highly soluble in 

 water, which takes up, at the comparatively low temperature of 48°, 

 about an equal weight. With increase of temperature the power of 

 solution is very much augmented, and at the boiUng point of the liquid 

 the capacity of water for dissolving sugar is almost unlimited. At the 

 degree of heat at which syrups are boiled down in the vacuum pan 

 (150° to 160°), water does not by any means possess this power of un- 

 limited solution. 



Fruit sugar is uncrystallizable, but forms, when dried in vacuo, at the 

 ordinary temperature of the air, a gummy semi-solid mass. It possesses 

 a peculiar action upon polarized light, which distinguishes it from grape 

 sugar, to which it is closely allied in many respects. I have never 

 found this variety of saccharine matter, as produced artificially, in a 

 pure state, but always mixed with cane sugar. It exists abundantly in 

 golden syrup, molasses, and treacle. Cane sugar refuses to crystallize 

 from a syrup which contains rather more than an equal weight of this 

 variety, and I have found that a syrup which contains less than eight parts 

 of cane to ten of fruit sugar is absolutely undrainable at any temperature. 



Grape sugar, as already stated, never occurs in any of the products of 

 the sugar manufacture. It crystallizes in fibrous masses or tufts ra- 

 diating from a centre, presenting a very beautiful appearance when 

 examined with a lens. The crystals are soft and minute, and no 

 definite crystalline form has as yet been ascribed to them. Grape sugar 

 is frequently called uncrystallizable sugar ; but this is evidently a mis- 

 nomer, arising from its being confounded with fructose. It has little 

 economic value, its sweetening power being 2\ times less than that of 

 cane sugar. Fruit sugar soon changes to grape sugar if no cane sugar 

 is present. We frequently find tufts of this substance in raisins and 

 other dried acid fruits, the skins of which have been ruptured. The 

 whiteness and viscousness of old honey is owing to the presence of 

 crystals of glucose. I have seen jelly and other preserves, in which all 

 the cane sugar introduced had been altered by heat and acid, become 

 opaque and semi-solid from the same cause. This phenomenon must not 

 be confounded with the much more common one of cane sugar forming 

 a hard crisp crust upon the surface of the jelly. 



