MILK-SUGAR. 293 



the whey on an average contains only about 4'8 per cent of milk- 

 sugar, while the sap of beet-root and sugar-cane contain more than 

 three times as much, the conditions for the manufacture are not of 

 such a nature as to be profitable; and, in addition to all this, the 

 limited uses of milk-sugar have to be taken into account. The 

 experience of the last twenty years has shown that the preparation 

 of milk-sugar from whey is not remunerative. It can only become 

 so if the business is carried out on a large scale. 



In the preparation of milk-sugar on a large scale, the whey is eva- 

 porated down in vacuum pans, either to the condition of a thin syrup, 

 and then the sugar is allowed to crystallize out, or it is evaporated 

 down till the sugar crystals separate out by means of centrifugal force 

 from the syrup. The residue is utilized for the feeding of swine, since it 

 is not worth while to recover, by osmosis, the sugar still remaining in the 

 syrup. 



In order to refine the raw milk-sugar, it is first of all dissolved in 

 water, the solution is then filtered, and to the filtrate there are added, for 

 every kilogram of sugar, three grams of sulphate of alumina and five grams 

 of milk of lime. The solution is then boiled for five minutes and filtered, 

 and in order to remove the colour the filtrate is passed through carbon 

 filters. The crystallization of the sugar from the solution is promoted by 

 the addition of alcohol. The sugar is obtained in the form of crystallized 

 sticks, which are obtained by suspending threads of cotton wool or thin 

 sticks of wood in the solution of sugar, and allowing the crystals to de- 

 posit round them, and is known as grape-sugar, in distinction to the sugar 

 which is obtained in the form of plates by allowing it to crystallize on 

 the bottom and sides of the vessel, which is known as flat-sugar. The 

 grape-sugar is purer than the flat-sugar. By repeated crystallizations 

 milk-sugar may be obtained in transparent glassy crystals, which possess 

 a retail value per kilogram of from 2-2 to 3-3 marks. 



Before 1880 there was only one dairy factory in Germany in which 

 milk-sugar was made, but since then Switzerland supplies all the milk- 

 sugar used. It is prepared in the summer-time in the Canton of Berne, 

 where neither the labour nor the fuel are especially expensive, by simply 

 evaporating the whey in cheese-kettles over an open fire. It is obtained in 

 the form of a gritty material, the so-called "sugar sand", which is of a light 

 yellowish gray colour, and is comparatively impure. The evaporation 

 of 500 kilograms of whey occupies about 24 hours. This sugar sand is 

 bought by merchants and refined. In the year 1876 it was valued in the 

 Alps at -6 to '7 marks per kilogram, while the value of grape-sugar and 

 flat-sugar, according to purity, varied from 1-12 to 1-3 marks per kilogram. 



