IDENTITY O F DEXTROSE FROM DIFFERENT SOURCES. 1691 CXV1.-The Identity of Dextrose from Diffemnt Xouwes, zciith Special Re ferenee to the Cupric Beduciry Po me?'. By CORKELILTS ~'SULLIVAN, F.R.S., and ARTHUR I J . STERS, D.Sc. r i 1 J-r I, numerow, and often discordant, numbers which different ob- servers hare published as representing the cupric reducing power of dextrose, as well as other facts which have been brought under our notice, led us t o speculate on the possible existence of two 01- more destroses, which, although closely agreeing in most of their proper- ties, might yet differ in others. I n order to elucidate this point, we prepared specimens of dex hose from different sources, and examined their principal properties. The specimens were purified by repeated crystallisation from dilute inethylic alcohol until the successive crops which separated from the1692 O’SULLIVAN AND STERN: THE IDENTITY OF solution possessed the same properties.were : Those carefully determined 1. The specific gravity of the aqueous solution. 11. The specific rotatory power. 111. The cupric reducing power. I. The specific gqsavity was determined at 15*5O, compared with that of water at the saiiic temperature, which was represented as 1000. For purposes of comparison, we divide the excess of the specific gravity of the sugar solution over 1000 by the number of grams of sugar dissolved in 100 c.c., and the factor thus obtained is called the divisor, and denoted by D ; it varies, of course, with the concentration of the solution. For any one sugar, the factor is a convenient indi- cator of the dryness.11. T h e speci$c yotatoryyozuer mas determined by means of a Laurcnt (sodium flame) polarimeter in a tube 200 mm. long at 15*5O, and cal- culated in the usual way. 111. The czcp~ic Teduciizg power was determined according to the directions previously laid down by one of us (O’Sullivan, J. Chenz. Soc., 1876, ii, 125). As is well known, the amount of reduction varies mate~ially according t o the conditions of experiment, and, con- sequently, we took especial care to work always under the same conditions, which were as follows : The Fehling solution wa.s prepared immediately before me ; 30 C.C. were diluted with 30 C.C. of water, and placed in a boiling water bath; from 0.12 to 0.13 gram of the dextrose under examination was weighed into a small beaker, dissolved i n 30 C.C.of water, and the solution raised t o the boiling point and quickly added to the hot Fehling solution ; the reduction was allowed to proceed in the water bath for about 10 minutes, and the precipitate filtered off by means of a Soxhlet tube; washed with water, alcohol, and ether; dried in a water oven, and weighed as cuprous oxide. We proved by the fol- lowing experiments that no oxidation of the cuprons oxide takes plaoe under these conditions : I. 0.1796 CuzO yielded 0.1590 Cu. Theory, 0.1594 Cu. ,, 0.2596 ,, 11. 0.1822 ,, :, 0.1616 ,, 7, 0.1617 ,, 111. 0.2925 ,, 7, 0.2600 9 , The Soxhlet tube eniploj-ed in these experiments has been modified by the insertion of a piece of platinum gauze at the point marked A in the figure.This renders the usual constriction at the base of the A 0 I IDEXTROSE FROM DIFFEREKT SOURCES, ETC. 1693 tube unnecessary. The filtering material is composed of the usual layer of fine asbestos. Tbis modification has been found easier t o pre- pare for filtration, and much more rapid in action than the usual form. In calculating the results. i t has been found convenient to adhere to the method laid down in the paper above referiwd to, and to cal- culate the " K " on the assumption that 1 gram CuO is reduced by 0.4535 gram of dextrose (1 gram Cu,O = 0.5045 gram dextrose). Tbe first specimen of dextrose examined had been prepared many pears ago from the inversion products of cane sugar; whether the cane sugar was derived from the sugar cane or the sugar beet we cannot now say.The crude dextrose was fractionally crystsllised from dilute methylic alcohol, and eight crops were obtained, which were examined with the following results : Grams per K. 1 5.359 3.805 54.3 103.3 - 2 6-489 3.840 53% 100.8 99.9 3 4.490 3.840 53-5 105.3 103.8 4 4TCO 3+49 53.2 104.6 104.5 5 4-643 3.834 53.0 103.0 106.0 6 4.335 3934 49.6 - - 7 5.703 3.823 50.6 - - 8 5.693 3.820 50.3 - - [.ID. 7-A- 7 Crop. 100 C.C. These experiments indicate that the product from which these crops were obtained was not pure. The next step was to recrys- taliise them with a view to obtaining a pure sugar. Crop 1 was dissolved ia dilute methylic alcohol, and a small crop (9) separated. Crops 2, 3, 4, and 5 were mixed, dissolved in dilute methylic alcohol, whereby crops 10 and 11 were obtained, the latter amounting to nearly half the original mixture.Crops 6, 7, and 8 were in the same way recrystallised, a crop (12) being obtained amounting to rather more than one-half of the original mixture. These crops were examined with the following results : Grams per K. 7 r--h-- Crop. 100 C.C. D. f a I D . 9 5.661 3.835 53.0 104.9 - - 10 10.502 3.814 52.8 104.1 - 105.9 11 10.088 3.825 52.4 102.9 104.6 104.2 12 9,715 3.832 526 103.9 - 102.6 We have here, without question, i n these four crops, one and the same substance in a state of practical purity, Laving [ a f D = 52.7 and K = 104.0. 5 x 31694 O’SULLLVAN AND STERN: TEE IDENTITY OF The next specimen of dextrose was prepared from a fairly pure commercial sample of cane sugar prepared from the sugar-beet.1000 grams were inverted by yeast at 60°, the inversion being normal. The filtered inverted syrup was concentrated under diminished pres- sure, dissolved in methylic alcohol, and from this a crystalline crop 8oon separated ; this WAS recryatallised several times from dilute methylic alcohol, and ultimately 130 grams of dextrose were ob- tained (crop 13). This was divided by fractional crystallisation from methylic alcohol into three crops (14, 15, and 16), which were examined with the following results : Grams per K. Crop. 100 C.C. D. [a]D. 7------ -7 13 8.968 3.822 527 105.0 106.3 14 10.154 3.823 52.3 105.4 105-0 15 10.392 3.830 52.8 104.2 103.7 16 9.66 7 3,827 52.5 104.4 103-7 These figures show that the whole crop (13) of purified dextrose was a pure substance, having [ a ] D = 52.6 aiid K = 104.7.The next specimen of dextrose was prepared i n exactly the same way from a sample of cane sugar obtained from the sugar cane. The purified dextrose was fractionally crystallised, yielding two crops, which were examined with the following reoults : Grams per K. Crop. 100 C.C. D. [a],,. -PA---- 7 17 9097 3.839 52.6 - 104.9 104-0 104.2 18 9.004 3.814 52.6 103.7 104.6 105.4 105.3 These are evidently fractions of a pure substance having [aID = 52.6 and I( = 104.6, and are identical with the pure dextrose already prepared. The next specimen of dextroBe was prepared from maize starch. A 25 per cent. starch-milk was acted on by 2 per cent. sulphuric acid at 100’ for three honrs, arid the solution, after removal of the sulphuric acid by baryta, was concentrated under diminished pres- sure, and the syrup dissolved in methylic alcohol.The dextrose was obtained in six crystalliaed crops. They were examined with tbe following results : Grams per Crop. 100 C.C. 19 7.974 20 9.460 21 8.429 22 8.169 23 8.183 24 9.054 K.+ 7 r-A- D. ra1D. 3.798 53.3 201.7 102.1 3.809 54.2 102.3 101.3 3.800 54.6 100.1 101.5 3.826 548 101.7 102.2 3.823 55.0 99.7 99.4 3.829 55.0 - - * We have in the K of these fract,ions at least some explanation how it waa that the K of doxtrose was put down at 100.DEXTROSE FRO11 DIFFERENT SOURCES, ETC. 1695 The syrup from which these separated was evidently a mixture ; Two large crops were the fractions wera mixed and recrystallised.obtained, which were examined as follows : Crop. 100 C.C. D. i a h . Grains per K. T--h-.-7 95 8.378 3.823 52.8 103.7 105.2 105.2 26 8.279 3.830 52.5 104.2 105.0 105.2 These two are evidently one and the same substance with [a]= = 52.65 and K = 104.7; and are identical with the pure dextrose pre- pared from cane sugar. Lastly, a specimen of dextrose was prepared from the inversion products of lactose. A solution containing 25 per cent. of pure lactose and 2 per cent. of sulphuric acid was heated a t 100' for two hours. The sulphuric acid wag then Feparated by bargta, and the filtered solution conceii- trated, under diminished pressure, to a syrup which goon solidified ; on treating this with methylic alcohol, the dextrose dissolved, leaving a residue of galactose.The dextrose mas then recrjstal- lised from water and examined, with the following results : Crop 27. 8.027 grams per 100 C.C. D = 3.834. [a]D = 53.9, agreeing fairly closely with the factors obtained above. It was recrystallised from methyh alcohol, when a first and large crop gave : Crop 28. 8.210 grams per 100 C.C. D = 3.829. [alD = 53.4. H = 106.2, 104.7, 105.4, 105.6, 103.6, 105.2. The experiments shorn that the samples of carefully purified dextrose prepared from f o u r different sources gave the following average results : Dextrose from cane sugar (of unknown origin) .... [ a ] D = 52.7, K = 104*0 cane). ..... [a]= = 52.6, K = 104.7 beet). ..... [a]D = 52.6, K = 104.6 3 7 ,: ), ,, (from sugar- 7 7 ., .) ), (from sugar- .. maize starch............ [aID = 52-65, K = 104.7 ,, .. lactose ................ [ a ] D = 52.4, K = 105.1 7 . It is evident tliai dl these dextroses have the same optical activity and K, and are apparently identical. The average of the above described experiments, and many others which we have not thought it necessary to record, give the following divisors for the specific gravity : 5.0 grams per 100 c.c.. ......... 3.840 10.0 ,, . . . . . . . . . . . . . . . 3.825 7.5 . . . . . . . . . . . . . . 3.8331696 POPE: A COJlPOUNI) OF CAMPHORIC AClD The figures which we hare obtailicd for the cnpric reducing power are higher than those which were given in the paper previously referred to ; the latter were made over 20 years ago, when the appli- ances for purifying the sugar were rery imperfect, and the limitations of the method not fully understood. Since then many observers have investigated the method, and amongst tllese the work of some stand out pre-eminent, on nccour,t of the care and thoroughness with which they have worked. We refer more particularly to the woyk of Soxlilet (J. p ~ . Chew,., [ a ] , 21, 227), Maercker ( 0 s ; . Uizg. Zeif. fu?. Zzcckey-iiad. und Landwidschcq?, 7, 699), and Allihn (J. p ~ . CJiem., 22, 55). Allihn’s figures appear to be in general use in Germany, mid onr experiments, although carried out’ in a slightly different manner, yet agree closely wit11 thern; this is shown by the figures given below. Mgrins. dextrose taken. Mgrms. cliprotis oxide obtai ricd. I---------- ---- 0 -043 0 *G84 0 *1265 0 *121 0 -127 0 -1 225 Mgrins. devtroso tables. K. found from Allihn’s ------- 115.0 0 *044 109.9 , 0 ‘085 104.1 0 *1245 104 -9 0 -12G 105.6 1 0.1225