The presence of invert-sugar is detected by the 

 copper test. Cane-sugar does not give the characteristic red 

 precipitate of Suboxide of copper (Cu 2 O) from alkaline solu- 

 tions of cupric tartarate, while glucose does. To estimate the 

 proportion of glucose present, a standard solution is used. 

 This is Fehling's solution. It consists of 90^ grains of sul- 

 phate of copper, 364 grains of neutral tartarate of potash, 

 4 fluid ounces of caustic soda of specific gravity 1*12 and 

 water to make up 6 ounces. In using this standard solution 

 it is brought to the boiling point and a known weight and 

 volume of solution of glucose dropped into it from a burette 

 until the copper has been just reduced which is known by the 

 blue colour being destroyed. The precipitate is then filtered 

 dried and weighed, the difference between its weight and 

 that of the sugar used in the solution gives the percentage 

 of cane-sugar. The quantity of sugar lost in reducing the 

 copper being glucose the residue is sucrose. Fehling found 

 that one equivalent (180 parts) of glucose decomposed 10 

 equivalents (i 246^8 parts) of sulphate of copper. There- 

 fore the percentage of glucose in the sugar solution = 



weight of the sugar solution x 100 



wt. of the soln. reqd. to reduce copper -j- wt. of sugar used 

 and the percentage of cane-sugar = weight of sugar used 

 minus percentage of glucose. Lactose behaves in the same 

 way as glucose with respect to Fehling's solution. 



592. A new process of refining brown-sugar (i.e. 9 musco- 

 vado) has been invented by M. Robin Langlois, a French 

 Engineer. Cane and beet sugar of the whitest and best 

 quality can be made by this process, which is still a secret. 

 The principal advantage of this system is that it is very 

 quick. 



593. Sugar is not made only from date-palm juice, sugar- 

 cane and beet. It is also obtained from maize-stalks, stalks 

 of sorghum saccharatum, cocoanut and toddy-palm juices, 

 and Bassia butyracia. In America the maple-tree is largely 



