PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 391 



of which the formula is €«, IT5, 0^, and which forms soluble salts with 

 nearly all the bases. 



1}lucic acid is also formed when a solution of cane or grape sugar is 

 ooiled for a long time with sulphuric or hydrochloric acid. 



It was not my intention at the commencement of tlie arrangement of this 

 paper to add much of any matter purely technical, but following is some 

 information which may not be uninteresting. 



The manufacture of grape sugar is a branch of considerable industrial 

 importance, the extent of which and interest attached to it, are, however, 

 very restricted, as it is less applicable to most of the purposes for which 

 sugar is required. It is only capable of being substituted for cane sugar 

 in a very limited number of cases, and will by no means supply its place 

 for sweetening tea, coffee or other alimentary substances, for to render the 

 two kinds upon an equality, in an economical point of view, five pounds of 

 grape sugar should only cost as much as two pounds of cane sugar. 



In the production of sugar from starch, on the manufacturing scale, 

 practice has confined itself to the use of sulphuric acid, because it is 

 cheaper, and after having effected its object is easily removed in a short 

 time. As all the varieties of starch arc equally adapted for the production 

 of sugar, the cheapest, or potatoe-starch, is only employed. The propor- 

 tions usually employed are 100 parts of starch, one to two parts of Eng- 

 lish sulphuric acid, and from 300 to 400 parts of water. The time required 

 for the conversion of the starch into sugar is dependent upon temperature 

 and quantity of sulphuric acid, and therefore ranges from two hours to two 

 days. At high temperature there is great danger of decomposing the 

 sugar also, by increasing the quantity of sulphuric acid. The best tem- 

 perature ranges from 212*^ to 219.5° F. 



When the starch and sugar manufacture are carried on together, the 

 starch is not dried, but the water which adheres to it is taken into account. 

 The acid is allowed to flow in a small stream into the water, and not the 

 water into the acid; the starch should also be added gradually. 



Starch sugar is chiefly employed for the manufacture of alcohol and 

 vinegar, to improve the quality of wines, etc. Many breweries, in France, 

 are connected with factories for the production of starch and sugar, which 

 is added in considerable quantities to their wort. This practice, however, 

 is considered by the English, who are the best judges, to be prejudicial to 

 the flavor of the beer. 



In the production of beet root sugar, which is absorbing considerable at 

 tention in this country at the present time, the agricultural part of the bu- 

 siness seems to require the most consideration. But it is not within the 

 province of this paper, if its limit would permit, to dwell upon it. 



From a number of examinations of the sugar beet, the following are the 

 mean quantities of matter constituting it: 

 96 per cent of juice, 

 4 do albumen, woody fibre and insoluble salts. 



100 



Of the 96 per cent, of juice, 10 per cent is sugar, 



3 do pectin, soluble salts, etc., 

 83 do is water. 



