§ 82. LEVULOSE. § 83. SACCHAROSE. 115 



tion, should produce no chauge in it ; another portion 

 should give no red coloration or precipitate with potassic 

 ferrocyanide, nor a black one "vvitli amnionic sulphide. If 

 these tests do not indicate a satisfactory termination of 

 the analysis, it should be repeated with a fresh quantity 

 of 10 c.c. of the cupric solution. 



The amount of solution of sugar required to reduce the 

 cupric oxide in this quantity of the cupric solution con- 

 tained 0.05 grm. of glucose. 



Generally, the first result obtained is only an approxi- 

 mation ; in the second trial, add at once nearly the whole 

 amount of sugar solution required, and then test the liquid 

 after each addition of two drops at a time. {Fresenius.) 



LEVULOSE. FKUIT SUGAR. CeH^Oe. 



82i This sugar is very soluble in water and aqueous 

 alcohol. It behaves like glucose with an alkaline cupric 

 solution, and is determined quantitatively in the same 

 manner. 



SACCHAROSE. CANE SUGAR. CisHsaOn. 342. 



83. This sugar is more soluble in water and aqueous 

 alcohol than glucose. 



It is not turned brown by strong alkaline solutions. 



If triturated with cold concentrated sulphuric acid, it 

 is turned black, and sulphurous acid is evolved. 



If a concentrated solution of saccharose is mixed with 

 cobaltic nitrate and a small quantity of fused caustic 

 soda, and boiled, a violet-blue precipitate is formed. The 

 presence of a very small quantity of glucose prevents the 

 formation of this precipitate. 



If sodic hydrate is added to a solution of saccharose, 

 and a few drops of cupric sulphate, a deep blue solution 

 is obtained that remains unchanged on standing in the 

 cold ; if the sodic hydrate is largely in excess, the solution 

 can be boiled a short time without change. 



