THE CONTROL OF THE FACTORY 559 



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

 with molasses of 40 gravity purity ? 



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



sucrose at 96 -3 = 96-3 (97-2-40) = ItQO fo 



sucrose at 97 2 97 2 (96 3 40) 



and the relative weights of the products are as 1-0066 X ~ : i, or as 

 1-0171 : i. 



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 purity, from which 

 sugar of 97 gravity purity is extracted ? 



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



97 - 40 9 6 



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

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

 per cent, sucrose and 97-3 purity. 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 , - ~~\ ~ 95 ' > an( ^ the weight of commercial sugar will 



be 1000 X - x - X - = 888 Ibs. 

 100 x ioo 96-3 



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

 obtained by 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 will 

 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, any 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 formulae are equally correct whether the solids used 

 in the purity calculations are absolute, gravity or refractive (cf. 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 dry 

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

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

 determining gravity purities in the juices, absolute purities in the sugar, 

 and refractive purities in the molasses. 



Control of the Sugar Boiling. In the more recently adopted methods 

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



