Nov. 3, 1887] 



NATURE 



The Ffynnon Beuno and Cae Gwyn Caves. 



I THINK it would be well for geologists and anthropologists to 

 allow the age of the deposits and stone instruments found at 

 these caves to remain an open question for the present. At 

 present I have had no opportunity of seeing any papers on the 

 subject, and I know of no opinions other than the one expressed 

 by Dr. Hicks, Nature, vol. xxxvi. p. 599. I am how- 

 ever fairly well acquainted with the glacial deposits of North 

 Wales and with Paleolithic implements, and I have seen the 

 caves and the tools found at and in them. My quite unbiased 

 opinion is and will so remain, — unless I get very convincing 

 proof to the contrary, — that the drift at the caves has been with- 

 out doubt relaid ; and is no more a true glacial deposit than the 

 valley gravels of the Thames. As for the tools — one in the 

 British !\Iuseum (South Kensington), and one in Denbighshire — 

 they belong to the very latest of Palaeolithic times, and might be 

 passed for Neolithic ; the Denbighshire example seen by me is a 

 knife-flake with fine secondary chipping up one edge. 



Dunstable. WoRTHiNGTON G. Smith. 



SYNTHESIS OF GLUCOSE. 



A NOTHER important acquisition to our store of 

 -^"^ knowledge has recently been made. Glucose, com- 

 monly called' grape-sugar, has been artificially prepared 

 by Drs. Emil Fischer and Julius Tafel in the chemical 

 laboratory of the University of Wiirzburg. This happy 

 achievement, which is announced in the number of the 

 Berichte just received, is one which has long been looked 

 forward to, and which cannot fail to give deep satisfaction 

 in chemical circles all over the world. As is generally the 

 case in syntheses of this description, not only has the sugar 

 itself been actually prepared, but, what is at least quite as 

 important, considerable light has been thrown upon that 

 much-discussed question — the constitution of sugars. A 

 most remarkable, and yet only to be expected, attribute 

 of this artificial sugar is that it is found to be entirely in- 

 capable of rotating a beam of polarized light. As is well 

 known, there are several naturally-occurring varieties of 

 glucose, all of which may be expressed by the same 

 empirical constitution CfiH]20(j, and all possessing the 

 power of rotating the plane of polarization : dextrose, or 

 grape-sugar, the best-known of these varieties, as its 

 name implies deviates the plane of polarization to the 

 right, as do several other less important varieties ; while 

 Isevulose, or fruit-sugar, rotates the plane to the left. But 

 in artificially preparing a glucose of the composition 

 QHj.jO,; there is just as much tendency for one kind to 

 be formed as another, and the probability is that both 

 dextro and laevo are simultaneously formed, and thus 

 neutralize each other, producing a totally inactive mixture. 

 It may be that, as in the case of racemic acid, the two 

 kinds are formed side by side and neutralize each other 

 in the solution ; or it may even be that, as is the case 

 with truly inactive tartaric acid, there is a true neutraliza- 

 tion within the molecule itself ; which of these hypotheses 

 is correct is a question for further work to decide. 



The substance employed as the base of operations was 

 acrolein, CHo^^CH — CHO, the aldehyde derived by oxida- 

 tion of allyl alcohol. The acrolein was first converted to 

 its dibromide, CH-jBr . CHBr . CHO, which was then 

 treated with cold baryta water, whereupon the bromine 

 was removed by the barium leaving the artificial sugar in 

 solution. The real difficulty was found to be in the isola- 

 tion of the sugar, but this was eventually overcome by 

 the use of phenyl hydrazine, CeHg . NH . NHj, which 

 forms a hydrazine compound of the formula C18H.22N4O4 

 with the new sugar, very similar to the compounds formed 

 by phenyl hydrazine with ordinary dextrose and laevulose. 

 This phenyl hydrazine compound was then found to yield 

 by reduction a base CgHi-jNOg, which, on treatment with 

 nitrous acid, parted with its nitrogen and left a syrupy 

 substance, possessing all the properties of sugars, and 

 distinguished only from ordinary grape-sugar by its optical 

 inactivity. 



The actual operations were f)erformed briefly as 

 follows : — 



.Seventy-five grammes of pure crystallized barium 

 hydrate were dissolved in a little over a litre of water, 

 and 50 grammes of previously redistilled acrolein dibromide 

 added drop by drop, the flask being continuously agitatecf, 

 surrounded by ice-cold water, for about an hour. In a 

 similar manner eight successive quantities were treated 

 until in all about 400 grammes of acrolein dibromide had 

 been converted into sugar. These eight separate portions 

 were then mixed, slightly acidified with sulphuric acid, 

 and the barium precipitated with a solution of sodium 

 sulphate. After removal of all the barium by filtration 

 the solution was neutralized with soda and evaporated 

 down to \\ litres. On cooling, a solution of 50 grammes 

 of the hydrochloride of phenyl hydrazine and 50 grammes 

 of crystallized sodium acetate in 100 cubic centimetres of 

 water were added ; after standing twelve hours a reddish- 

 brown resin separated out and was removed by filtration. 

 150 grammes more of phenyl hydrazine hydrochloride 

 and the same quantity of sodium acetate were then 

 added, and the solution warmed upon a water-bath ; 

 after again standing some time the solution became 

 turbid, and in course of four hours a dark-coloured pre- 

 cipitate, partly crystalline and partly resinous, separated 

 out. After washing and drying, and subsequent agitation 

 with ether and trituration with alcohol to remove organic 

 impurities, and extraction of the inorganic salts by hot 

 water, the phenyl hydrazine compound was finally 

 isolated. 



Analysis of the recrystallized compound indicates that 

 its composition is Q8H22N4O4, and its properties are 

 very similar to those of the phenyl hydrazine compound 

 of ordinary grape-sugar, the melting-points of the two 

 bodies being identical, 205'' C. It is almost insoluble in 

 water, ether, and benzene, and only with difficulty soluble 

 in hot alcohol ; it is more soluble in glacial acetic acid, 

 but the solution soon becomes dark red. It crystallizes 

 from hot alcohol in pretty little prism aggregates, while 

 the ordinary grape-sugar compound crystallizes in 

 spherical aggregates of fine needles. It is further dis- 

 tinguished from the latter compound inasmuch as a layer 

 20 cubic centimetres thick, is without action upon a beam 

 of polarized light. 



When reduced by means of zinc dust and acetic acid, 

 a base was produced analogous to the one formed by the 

 reduction of the corresponding phenyl hydrazine com- 

 pound of grape-sugar. This base was difficult to isolate, 

 owing to the non-crystallizable nature of its acetate ; the 

 fact was fortunately discovered, however, that its oxalate 

 was crystalline, and readily obtained pure. Hence its 

 analysis has been effected, and the numbers found point 

 to the composition (C6Hj3N05)2 . C2H2O4. This base 

 reduces Fehling's solution strongly on warming, and with 

 phenyl hydrazine regenerates the parent compound ; but, 

 once again, is optically inactive. 



Finally, by the action of nitrous acid, nitrogen at once 

 began to be evolved, and when the evolution ceased the 

 liquid was neutralized with soda, evaporated in vacuo., 

 and the residue extracted with alcohol. On evaporation 

 of the alcohol the sugar was left as a bright brown syrup, 

 free from nitrogen and ash, of sweet taste, and capable of 

 instantly reducing Fehling's solution. 



Up to the present time two hypotheses as to the con- 

 stitution of sugars have pretty evenly balanced each 

 other. According to one, sugars are considered, in virtue 

 of their power of reducing ammoniacal silver solutions, 

 as aldehydes containing also alcohol groups ; on these 

 lines grape-sugar would be formulated, CHgOH — 

 (CHOH)4-CHO. But it has since been shown that, 

 the property of reducing ammoniacal silver solutions 

 is not confined to aldehydes, for the series of bodies 

 known as ketone alcohols also possess it ; hence grape- 

 sugar may also be written CH2OH— (CH0H)3— CO— 



