THE CONTROL OF THE FACTORY 559 



97-2 gravit}' purity, which can be obtained from a juice of 80 gravity purity 

 with molasses of 40 gravity purity ? 



From formula 11 the relative quantities of sucrose in the sugars are 

 sucrose at 96-3 96'3 (97" 2— 40) 



sucrose at 97-2 97 2 (96-3—40) 



= I -0066 



97 



and the relative weights of the products are as i-oo66 X ^ : i, or as 

 1-0171 : I. 96 



2. What weight of molasses of 40 gravity purity and 96 gravity solids 

 will be obtained from 100 tons of juice of 18° Brix and 84 puritj-, from which 

 sugar of 97 gravity purity is extracted ? 



From formula 7 the answer is 18 X ^ X —r =2-28 tons. 



97-40 96 



3. 1000 lbs. of low grade sugar of composition sucrose 90 per cent., 

 absolute purit\^ 92, are to be melted and produced as 96 test sugar of 96-3 

 per cent, sucrose and 97-3 purit}^ What quantity will result ? 



It is necessary to assume a purity for the waste molasses ; let this be 

 45 absolute. Then from formula i the percentage recovery of sucrose will 



be 100 X — -~^ r = 95 ■ o. and the weight of commercial sugar will 



92-0 (97-3 -45) yj & 5 



be 1000 X 9£ X 95 X ^ = 888 lbs, 

 100 100 96-3 



An additional control over the operations in the boiling house may be 

 obtained b}^ constructing dry substance balances, based on absolute solids, 

 gravity solids or refractive solids. From the difference between the solids 

 balance and the sucrose balance, a non-sugar balance is obtained, in which, 

 however, will appear all the experimental errors. In the application of 

 such balances to control, the following points are to be borne in mind. 

 Mechanical loss of material before the removal of sugar from solution \\ill 

 result in an equal proportionate loss of sugar and non-sugar, but after sugar 

 has been removed any loss gives a disproportionate loss of non-sugar. A 

 means is thereby afforded of locating the position of mechanical loss. 



On the other hand, an\' sugar lost by inversion or caramelization goes to 

 swell the amount of non-sugars, so that an exact balance in the non-sugars 

 may result from a compensation of errors. 



The Basis of Reference for Purities. — The system of control described 

 above and the various formula are equally correct whether the solids used 

 in the purit}^ calculations are absolute, gravitj' or refractive (c/. Chapter 

 XXV), provided that in the last two cases the determinations are made in 

 equal concentrations of non-sugar. The writer's opinion is that gravity 

 purities form the most convenient basis since the specific gravity can be 

 determined with ease and with far greater accuracy than can either the dr}^ 

 substance or the refractive index. WTiatever basis is selected must be used 

 throughout, as the control is vitiated if the bases are mixed, as, for instance, 

 determining gravitj' purities in the juices, absolute purities in the sugar, 

 and refractive purities in the molasses. 



Control of the Sugar Boiling. — In the more recentty adopted methods 

 of sugar boiling the procedure is based on making the strikes at certain 



