26 KANSAS ACADEMY OF SCIENCE. 



OBSERVATION OF THE FORMATION OF SUGAR CRYSTALS IN THE 

 JUICE OF SORGHUM SACCHARATUM. 



BY E. B. COWGILL. 



In effecting the crystallization of sugar from the juice of sorghum saccharatunv 

 I observed carefully, with the aid of a lens, the several stages of the process. 



The juice was first defecated by the usual lime process, and then reduced to a 

 density, while hot, of 20° B. A portion of this liquid was introduced into a small ex- 

 perimental vacuum-pan. The vacuum was maintained at about 24 inches mercury 

 by a spray of water in a receiver, and by hand pumping. Heat of a coal fire was 

 applied through a water bath. The temperature remained at about 140° F. Oppor- 

 tunity was not available, except as hereafter noted, for determining the specific 

 gravity of the syrup at the time crystallization commenced, but the sugar-boilers' 

 usual test of drawing samples of the hot syrup between the thumb and fingers was 

 made repeatedly. When the fibers thus drawn reached a length of about two and a 

 half inches the syrup showed under the microscope a slight turbidity or cloudiness, 

 somewhat resembling the effect produced by allowing a few drops of milk to fall into 

 a glass of water. Examination by transmitted light showed the particles of the 

 little cloud to be crystals, able to refract and reflect light. These crystals were so 

 minute that no forms could be described, nor could they be discovered to have ap- 

 preciable size; and only by their action upon light, which from its delicacy might 

 easily have escaped observation, could the beginning of the crystallization be de- 

 tected. Another phenomenon which usually precedes crystallization, and is often 

 seen after the formation of microscopic crystals has taken place, may be easily con- 

 founded with crystallization: When a sample is removed from the vacuum-pan and 

 placed upon glass for observation, the surface becomes cooled and somewhat rigid. 

 As the reduction of temperature reaches the interior portions, contraction ensues, 

 and with it minute flexures of the already cooled surface. These flexures refract and 

 reflect light strongly, and these effects are liable to be mistaken for or to overshadow 

 the less prominent but more beautiful effects of the crystals. A more unpardonable 

 error is to mistake for crystals the curious-looking gaseous bubbles of various sizes 

 which precede crystallization and sometimes continue long after the appearance of 

 the cloud of microscopic crystals. 



To increase the size of the infant crystals it is only necessary to "feed" them. 

 Having continued the concentration of the syrup, in vacuo, until, by the thumb-and- 

 finger test, fibers may be drawn four or five inches long, a small portion of fresh 

 semi-syrup was added. No new crystals appeared to be formed from this fresh ad- 

 dition, but a portion of the sugar it contained seemed to gravitate to the micro- 

 scopic crystals of the first portion. The growth, however, was so inconsiderable 

 that only after several successive additions could the crystals be seen to have either 

 size or form. The action upon light, however, became more distinct at each addi- 

 tion. What at first might have been confused with the refraction and reflection of 

 the crumpled surface, or even with the shimmer of a liquid surface, was discernible 

 even by unpracticed eyes as the true crystalline refraction and reflection. After a 

 few more additions the clouded appearance was lost. Now a sample viewed through 

 the lens by reflected light appeared like a miniature bank of fine, yellowish sand; 

 the forms of crystals were distinct as they lay piled one upon another in the syrup. 

 So greatly was I elated at this stage of my first experiment that the thermometer 

 was neglected, and before it was suspected the temperature had risen to 160° F., and 

 the crystals all disappeared. To renew them and again build them up to their 

 former size was a work of several hours. This being done, the process of feeding 



