Vol. IV. No. 7i 



THE AGKICULTURAL NEWS. 



99 



SOME CHANGES 



Of recent 



OCCURRING IN 

 years two facts 



COMMERCIAL SUGARS. 



of importance to sufjar 



POLARIZATIONS AT VARIOUS DATES. 



planters in these islands have been observed (ii) that sugar 

 is sometimes met with which gives a much lower polariscopic 

 test than experience would lead one to expect, and (6) that 

 some samples of sugar are found to be undergoing changes 

 in polariscopic test. Observation suggests that there may 

 probably be some connexion between these facts. 



It is well known to muscovado sugar boilers that at 

 times the syruii, towards the final stages of boiling, will foam 

 and boil with difficulty, this being more frequently the case 

 with juice obtained from canes grown ui)on dry places, such 

 as hillsides, with a thin coating of soil and more [larticularly 

 in dry seasons. Certain fields on many estates are known 

 by those in charge of them to be liable to produce juice 

 which will '.scorch' in the process of manufacture. I believe 

 it is the sugar produced from juice of this nature which is 

 liable to yield sugar testing polariscopically considerably 

 below what one would expect. 



With normal sugar an experienced observer can estimate 

 the polariscopic test with a fair degree of accuracy. These 

 abnormal sugars, therefore, are a source of disappointment 

 to the producer who, not infrequently, and perhaps not 

 unnaturally, inclines to and expresses the view that the 

 abnormal test is due to errors on the part of the chemist. 

 I have myself examined samples of sugar which have given 

 results from 2° to 3" below what experience in handling 

 sugars led me to expect. One concrete example will suffice. 



A sample of massecuite from juice of the kind referred 

 to above was kindly forwarded by the manager of a sugar 

 estate in Antigua. The sugar was cured in an efficient 

 laboratory centrifugal : muscovado sugars so cured usually 

 have a polariscopic test of about 92° and under ordinary 

 circumstances one would have expected the sugar in question 

 to have tested about 92°. It actually tested 88-8 or over 

 3° below reasonable and skilled expectation. From a monetary 

 point of view this would mean that the sugar would sell for 

 some 8s. per ton less than a skilled manager would lia\e 

 reason to expect. One cannot wonder at disappointment. 



This peculiarity appears to be due to the presence in the 

 juice of some unknown constituent which we can only 

 describe as ' gum.' These abnormal sugars will therefore be 

 referred to as ' gummy ' in what follows. 



Fermentive changes are frequently observed in samples 

 of muscovado sugar ; a peculiar and easily recognized aroma 

 is produced and considerable quantities of gas are given oft". 

 When these changes take place in tightly [lacked, pasty sugar 

 the evolution of gas causes the mass to become spongy and to 

 rise like dough, so that the .samples not infrequently expand 

 beyond the confines of the tins or bottles in which they are 

 placed. Experiments to demonstrate this expansion have 

 been made repeatedlj- in the laboratory by packing the sugar 

 in glass cylinders; in the course of a few hours considerable 

 expansion is often observed, while in some cases the sugar 

 has been forced far beyond the top of the containing cylinder. 

 In most cases, however, when the sugar is loosely packed or 

 ■where, as in the bags and hogsheads in which it is stored, 

 there are numerous air spaces whence the molasses have 

 drained, the gas escapes without difficulty and no visible 

 change takes place. Repeated polariscopic testing has brought 

 to light an unexpected feature of these fermentive changes. 

 In the early stages of the process the polariscopic test of 

 the sugar steadily rises : this takes place when the sugar is 

 kept in glass vessels and is not due to the draining away of 

 molasses. After a time the process is reversed and a steady 

 fall in test takes place. Some examjiles will show the nature 

 and extent of these changes. 



1^ 



86-7 



88-4 

 87-2 



a 



1-5 



86-4 

 88-2 

 86-9 



3 



86-1 



88-0 

 86-7 



3 

 1-5 



86-3 



87-6 

 86-4 



1-5 



86-8 

 87-4 

 86-3 



3 



< 



84-9 



8.5-4 



83-5 

 83-0 



The changes in polariscopic test in the sugars under 

 examination have not been uniformly regular: this is 

 probably due to disturbances resulting from the removal of 

 the sugars from the bottles and their thorough stirring in 

 a mortar before each test was made. Speaking generally, 

 there is a period of rise followed by a period of fall. In the 

 case of No 1. the rise is from 86'1° to 869^, that is 0"8°, 

 subsequently falling to 83'5°, or 3'4° below the maximum, the 

 observation extending over 171 days. 



In No 2. the rise is from 88'0° to 88'5°, or 0'5°, the 

 minimum observed was 87'4', or W below the maximum, 

 the observations extending over 85 days. 



In No. 3 the observed rise is from 869° to 87"9°, falling 

 subsequently to 83'0°, or 4'9' below the maximum. 



These three cases were those of commercial samples 

 which were received in a fermenting condition; it is only 

 reasonable, therefore, to infer that the examination began 

 during the period of rise, and that the rise in test observed is 

 only a portion of that which actually took place so that its 

 full extent is not shown ; the probability is that it is much 

 greater. 



The changes observed in the case of the sugar prepared 

 by means of the centrifugals were as follows : — 



This sugar was much freer from molasses than an 

 ordinary sample of muscovado sugar : the original polaris- 

 copic test, 888', was far below what the appearance of the 

 sugar would lead an experienced observer to expect. The 

 test steadily rose to 91 '6', a rise of 2'80°: a rapid fall to 

 91-3 followed, succeeded by a slow decline to 91-0°.* 



In another instance the following changes were 

 observed : — 



* Comidete analyses of this sugar were made at the time 

 when each polariscopic test was ascertained. The discussion of 

 the changes indicated is reserved for the present ; tho chemical 

 nature cf tlie changes will be dealt with in a subsequent paper. 



