202 



SCIENCE. 



[Vol, XIV. No. 346 



the peculiar qualities of lacquer make it seem worthy of more con- 

 sideration than it has received in this country. It gives a surface 

 to wood much harder than our best copal varnish, without brittle- 

 ness. It takes a polish not to be excelled, which lasts for centu- 

 ries, as may be seen in the old treasures of Japan. It is proof 

 against boiling water, alcohol, and, indeed, it seems to be insoluble 

 in every agent known. It is the best possible application for lab- 

 oratory tables. I have a set of photographer's developing trays 

 that .have been in use for more than a year, and I find them excel- 

 lent and cheap. In Japan it is used for many household articles. 



A very serious objection to the use of lacquer in this country is 

 the danger of lacquer-poisoning from the fresh material. I have 

 recently heard of a piano-maker who tried to use it, but it affected 

 his workmen so seriously that he was obliged to give it up. The 

 Japanese are very much in dread of the poison, as I found when I 

 ■tried to get some of my students to accompany me as interpreters 

 to the places of manufacture. Those who are subject to the 

 poison suffer precisely as patients afflicted by the Rlnis, or poison- 

 ivy. Of course, those engaged in lacquer-work are not affected by 

 it; but whether one acquires immunity after a time, I am unable to 

 tell. However, if the poison is a volatile acid, it would seem pos- 

 sible to remove it by a heat that would leave the lacquer uninjured, 

 and thus make it available for use in this country. 



THE PRODUCTION OF SUGAR. 

 Before proceeding to describe the processes adopted for the 

 extraction and refinement of sugar, says Ward Coldridge, in a 

 sequel to an article on the same subject reprinted from Knowledge 

 in Scietice of Aug. 30, it will be advisable to explain the difference 

 between what a chemist means when he speaks of " a sugar " and 

 what people generally understand by sugar. The chemist uses 

 sugar as a generic term, and includes under it — strange as it may 

 seem — things which have no sweetness, and excludes the sweetest 

 of all substances, the newly discovered saccharine. He subdivides 

 his sugar into two classes, — first, true sugars, which are distin- 

 guished by their power of undergoing alcoholic fermentation ; and, 

 secondly, bodies which do not suffer fermentation. Recent research 

 has diminished the number of substances of the second class, so 

 that for the purpose in hand this class can be eliminated, and our 

 attention can be fixed on the first group only. These fermentable 

 substances which yield alcohol are typically represented by grape 

 sugar and cane sugar. Now grape sugar is less sweet than cane 

 sugar, and its chemical constitution is different. Grape sugar has 

 the formula C^HjjOc ; that is, its molecule contains six atoms of 

 carbon, combined with twelve of hydrogen and six of oxygen. 

 When suitably treated with yeast, it ferments, and forms alcohol, 

 and evolves a part of its carbon and oxygen as carbonic acid, one 

 of the two substances from which the plant originally began to 

 form its sugar. The equation is, 



CsHjaOe = 2CsHeO -f 2 CO3 



Grape sugar Alcohol Carbonic acid. 



It will be remembered that the plants originally formed their 

 sugar from water and carbonic acid ; and now it can be understood 

 that Nature, when she wishes to dispose of an excess of sugar, 

 transforms it into alcohol and carbonic acid. There is thus a re- 

 version to the original type : — 



Water ^ i Alcohol 



and > > Sugar > J. and 



Carbonic acid ) ( Carbonic acid 



But alcohol takes the place of water. In the face of the wide dif- 

 ference between the actions of water and alcohol on humanity, it 

 may seem absurd to say that the final products bear any resem- 

 blance to the original. Yet, in spite of the physiological difference, 

 the chemical relation of alcohol to water may be summed up in the 

 statement that alcohol is water in which one of the two hydrogen 

 atoms are replaced by a group of carbon and hydrogen atoms, 

 " CsHb." Thus, 



Water. . 

 Alcohol. 



H. OH 

 C„H,. OH 



Nature does not, however, desire to flood the world with alcohol, 

 for she very quickly transforms it, by aid of a countless army of 



minute living organisms, into vinegar ; and thence, in turn, she 

 passes back to what she started from, — to water and carbonic 

 acid. So the cycle of changes runs on ; in all stages it is always 

 proceeding. 



The conversion of common sugar is not so direct. Cane sugar 

 must drink water before it can form alcohol. But the draught of 

 water acts on it chemically, and converts this form of sugar into 

 two others, one of which is uncrystallizable. When the sugar be- 

 comes thirsty at the temperature of the West Indites, it absorbs 

 water with greater eagerness, and as a result a quantity of mt>^ 

 lasses or treacle is formed. 



The older method of extracting the sugar — and in future in this 

 paper the word will be used in its commercial sense only — was to- 

 take the canes which had been cut off as near the roots as possible 

 and stripped of their leaves, and to crush them. From the crushed 

 canes the juice exuded. This juice held in solution, besides the 

 sugar, various substances of an albuminoid nature containing nitro- 

 gen, and of mineral bodies chiefly that phosphate of lime (CajaPO,) 

 which is obtained from bones. The object of the process is to 

 remove these foreign substances, so as to have command of a 

 comparatively pure solution of sugar in water. The albuminoids 

 must be removed as quickly as possible, for they soon begin to as- 

 sert their presence by causing fermentation in a manner analogous 

 somewhat to yeast. The plan adopted is to collect the juice in 

 large tanks, and then to add a small quantity of lime. The liquor 

 is next heated to a suitable temperature; a thick scum forms on 

 the surface. When it is considered that this coagulation of the 

 albuminous substances has proceeded far enough, the clear liquor 

 is drawn off from below. From this solution the manufacturer 

 desires to obtain as much sugar as possible by crystallization. He 

 therefore boils off the water quickly in open copper vessels, and in- 

 cidentally improves the purity of his product by removing such 

 scum as may form. The thick sirup which remains is run into 

 coolers and allowed to stand until no more sugar-crystals separate. 

 Finally he places the magma of crystals, and the mother-liquor 

 from which the sugar has separated, into casks with perforated 

 bottoms. The uncrystallizable thick brown viscid mother-liquor 

 which draws away is the common molasses or treacle which is 

 chiefly used in the manufacture of rum. 



The process which has been thus outlined is far from being 

 economically perfect. In fact, it is extravagant and wasteful. To 

 begin with, the mechanical contrivances generally used by the 

 colonial sugar-planter for crushing his canes are not perfect : he 

 might obtain more juice from a given weight of cane. A some- 

 what recent invention seems to have a future before it in this direc- 

 tion. The principle is very simple and well known. It utilizes the 

 fact that a body, when rapidly whirled around, will fly oft tangen- 

 tially unless restrained. The machinery is here so arranged that 

 the juice may escape, but the solid pulp is restrained, and at the 

 end of the operation is left in a dry condition. 



However, the most serious defect of the above process arises in 

 the actual manner of working up the comparatively pure sugar 

 solution. Above it was said that the manufacturer rapidly boiled 

 off the water ; of course economy of time is an element to be con- 

 sidered. Allowing, then, that the water is removed quickly, it may 

 seem at first sight that the process is excellent. But as a fact -it is 

 very wasteful. Why it should be so will be understood by realii- 

 ing the fact that at the temperature used the water is not merely 

 evaporated, but that some enters into combipation with the cane 

 sugar and converts it into grape sugar, as given above, and in the 

 final result a large proportion of molasses is formed. So the ques- 

 tion has been considered whether it is possible to remove this water 

 under such conditions as will prevent, or at least diminish, the 

 chemical change. The answer has been an affirmative OTie. The 

 liquor, instead of being concentrated by boiling down under at- 

 mospheric pressure, is now heated in vessels from which the air 

 can be exhausted. Consequently, according to the well-known 

 connection between the temperature at which water boils and the 

 pressure on its surface, the temperature of ebullition in a vacuum 

 will be much lower than in air ; the sugar solution wUl thus be 

 kept while concentrating at temperatures below that at which it 

 readily drinks water, and becomes in part uncrystaUizable. 



At the present time the colonial sugar manufacturer is proving 



