PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 389 



ment of the impure eyrup in the crystalline mass by passing pure syrup 

 through it. The product is refined sugar'. 



Chemically pure sugar is snow white, free of odor, and of a density of 

 1'66. It crystallizes in oblique four-sided prisms, terminated by two con- 

 verging planes, or derived figures. In this form it contains 5'3 per cent, of 

 water of crystallization. It dissolves in any quantity in water at 212 

 degrees, and in one-third of its weight of cold water. A heat of about 320 

 degrees fuses it; and at a red heat it burns with a vivid white flame. 

 When subjected to dry distillation it yields water, pja'omusic acid, car- 

 bonic acid, and carburetted-hydrogen. It is unalterable by any exposure 

 at the ordinarj'^ temperature of the atmosphere. When sugar is melted at 

 320 degrees, it forms a viscous mass, flowing with difiiculty, which solidi- 

 fies into a transparent mass having a vitreous fracture. This mass, rolled 

 out on marble tables, is sold under the name of barley sugar ; in making 

 which confectioners are in the habit of adding a small quantity of vinegar 

 before melting the sugar. Melted sugar kept for some time at a tem- 

 perature of 356 degrees loses the property of crystallizing when re-dissolv- 

 ed in water; and its constitution is in such case altered. 



The composition of crystallized sugar and that of barley sugar, according 

 to Regnault is C12, Hn, On. 



The mineral acids, and a greater part of the organic acids, alter cane 

 Bugar so that in its chemical properties it nearly resembles fruit sugar. 

 These acids which produce the transformation undergo no change in them- 

 selves, but are found intact in the liquor. 



Cane sugar combines with bases, and forms, in certain cases, crystalliza- 

 ble compounds, called saccharates. 



The presence of sugar prevents the precipitation of several metallic oxides 

 by alkalies. 



If sugar is subjected to prolonged action of nitric acid, a great deal of 

 oxalic acid is formed, which is finally converted into carbonic acid. 



At the boiling point sugar reduces several metallic salts. It precipi- 

 tates sub-oxide of copper, (Cua 0) from the acetate of copper, and metallic 

 copper from the sulphate and nitrate of this metal ; and it precipitates 

 metallic silver from the solution of nitrate of silver. 



Under the influence of yeast, rennet, casein, and protein compounds 

 generally, sugar loses its sweetness, and is transformed into liquid sugar, 

 gum, lactic and butyric acids, mannites, glucose, and ultimately into alco- 

 hol and carbonic acid. Each of these transformations is a successive step 

 towards the completion of the fermentation. 



The proper proportions to insure a successful fermentation are 1 sugar, 

 5 water, and 1 yeast, and a temperature 80° to 90°. 



The adulterations of sugar are numerous ; but easily detected. The 

 most important sophistications are the admixture of pure sugar with lime, 

 or with the natural impurities which constitute raw sugar. Lime is 

 detected in the solution by a white precipitate being caused by oxalate of 

 ammonia. The admixture of grape sugar with cane sugar may be detected 

 by mixing bichromate of potash with a syrup of the sugar to be examined, 

 and heating the mixture to the boiling point, in a teal tube, and then 

 removing from the heat. If the cane sugar is pure a deep green color will 



