Dex. 15, t879] 
NATURE 
2 
13 
7 

CHEMISTRY 
Constitution of Arbutin 
Huco ScuirF has made some interesting experiments relating 
to the constitution of arbutin. This substance splits up into 
glucose and hydroquinone, just as salicin is resolvable into 
glucose and saligenin (Strecker). The relations between salicin 
and arbutin may be represented by the following formula: 
O {oO 
C,H, } (OH) CoH, ) (OH), | 
6°*7 4 | 
{0 Laat go 
CeHs) cH,. OH CeHs) on 
Salicin (Glycosalicyl alcohol). Arbutin ( Glycohydroquinone). 
The hydrogen in the oxbydryls of the glucosic portion of 
arbutin may in fact be replaced by acid radicals, just as the author 
formerly showed in the case of salicin (Zeitschr. (2), v. 1. 52). 
Moreover, the hydrogen belonging to the hydroquinone in arbutin 
is easily replaceable ; whereas in salicin the hydrogen belonging 
to the saligenin is not capable of substitution. 
Benzoyl-arbutins are obtained by means of benzoyl chloride ; 
acetyl-arbutins, with acetyl chloride or acetyl oxide, which act at 
60°—8o0°. The ultimate products of the reaction separated from 
the resulting solutions, after cooling, by means of ether, contain 
five acid radicals, and have this composition : 
Caen? 
0 
Ce; } (0. C,H;0), iO. GEO), 
{O ,O 
CeHi) 0. C,H,O CeHs) 0. C,H,O 
Pentacetyl arbutin. Pentabenzoyl-arbutin. 
They are colourless bodies, insoluble in water, slightly soluble 
in ether, more soluble in hot alcohol, from whence they crystallise 
on cooling in small shining needles. The acid radicals may 
easily be taken out again by boiling with weak bases. Together 
with the pentabenzoylated compound, the author likewise ob- 
tained dilenzoyl-arbutin, in which the hydrogen might be further 
replaced by acetyl. 
Dinitro-arbulin dissolves easily in acetic oxide, and is con- 
verted into 
oO 
C,H, } (O. C,H,0), 
Pentacetyl-dinitro-arbutin oO 
C,H,(NO,), 
GOCE 0) oimteae a0) 
which may be separated from the acetic acid solution by water, 
and crystallised from hot alcohol in fine needles, insoluble in 
water, slightly soluble in ether. The alcoholic solution heated 
with sulphuric acid yields glucose, acetic ether, and dinitrohydro- 
quinone, easily recognisable by the splendid colour which it gives 
with caustic alkalies. Dinitro-arbutin forms with basic lead 
acetate a crystalline orange-coloured lead-compound, in which the 
hydrogen of the oxhydryl is replaced by lead. Arbutin gives no 
precipitate, even with an ammoniacal solution of lead-acetate. 
Recently precipitated silver-oxide is reduced, even at ordinary 
temperatures, by an aqueous solution of arbutin. On adding 
freshly prepared silver carbonate to a solution of arbutin heated 
to 50°—60° as lony as carbonic acid is evolved, and heating for 
a short time with excess of the silver carbonate, a yellow solution 
is obtained, which no longer contains arbutin; but on separating 
the dissolved silver with a few drops of hydrochloric acid, and 
filtering, a solution is obtained, from which alcohol precipitates 
white flocks consisting of a compound formed by the union of 
2 molecules of arbutin minus 2 atoms of hydrogen, viz.— 
C,H,0 (OH), 
Diarbutin O 
(GAS 
or SOO als ai cue tere 
cH.j° } ‘ 
; err | 
Glycoquinhydrone \ O 
CoH7° | (OH), 
This compound may be regarded as the glucoside of quin- 
hydrone (green hydroquinone) ; it is related to arbutin in the sime 
manner as helicoidin to salicin. Glycoquinhydrone is not at all 
bitter ; it forms acetyl-derivatives when treated with acetic oxide, 
and an orange-coloured nitro-product with nitric acid. The 

latter, when decomposed in alcoholic solution by sulphuric acid, 
does not yield any substance that turns violet with potash. By 
means of zine and sulphuric acid, hydrogen may be again added ; | 
and dinitro-hydroquinone thereby produced. 
A solution of arbutin produces with ferric chloride a deep blue 
colour, which gradually disappears. None of the derivatives of 
arbutin above described exhibit this reaction. 
Schiff also finds that amygdalin contains seven, and phlorizin 
five oxhydry] atoms, the hydrogen of which may be replaced by 
acetyl. Hence he assigns to these bodies the following formule ; 
\ O ( O 
C,H, ( (OH), C,H, } (OH), 
O oO 
C,H, \ (OH), C,H, OH 
i) Q) \ oO 
O C,H ‘ 
CH | Gn Bel COmOE 
Amygdalin, Phlorizin. 
(Zeitschr. f. Chem. (2) v. 519. Ann. Chem. et. Pharn, cliv. 237.) 


SCIENTIFIC SERIALS 
Poggendorff’s Annakn, 1870, No. 7. The contents of this 
Number are :—(1.) ‘‘ On the effect of Roughness of Surface on 
the Radiation of Heat,” by G. Magnus. The author shows that 
the generally accepted explanation of the increased emission of 
radiant Heat by roughened surfaces, that it depends on a dimi- 
nution of superficial density, is inadmissible. He attributes it to 
tie refraction which takes place at the surface of emission, whereby 
the direction of the rays which leave the surface obliquely is 
changed. (2.) ‘“‘On the Specific Gravity of Alcohol and of 
Mixtures of Alcohol and Water,” by E. H. Baumhauer. <A 

2. 
| defence of the author's tables of the specific gravity of alcohol 
against Mendelejeff’s criticisms contained in Poggendorff’s 47- 
| walen for 1869, vol. 138. (3.) “On the Flow of Mercury through 
Capillary Tubes,” by E. Warburg. The author’s experiments 
prove that in glass tubes, ‘whose diameter is a sufficiently small 
fraction of their length, the quantity of mercury which flows 
through them in a given time is directly proportional to the diffe- 
rence of pressure at the two ends, to the fourth power of the diame- 
ter, and inversely proportional to the length, but that it is indepen- 
dent of the absolute pressures at the ends so long as the difference 
remains constant. He concludes from these results that there is 
no friction, under the conditions of the experiments, between the 
mercury and the glass, but that the film of mercury in contact 
with the glass remains at rest while the inner portions flow 
throughit. (4.) ‘‘ Continuation of Investigations into the Electro- 
motive Force between Liquids,” by J. W. Miiller. (5.) ‘On 
the Determination of the Proportion of Water in Glacial Acetic 
Acid,” by F. Riidorff. The author gives a table for deducing the 
proportion of water contained in acetic acid from the freezing 
point of the mixture. He gives 16°7° C. as the freezing point of 
pure acetic acid (without water), and finds that the presence of 
4 per cent. of water lowers the freezing point by more than a 
degree. (6.) ‘‘On the Determination of the Freezing and Melt- 
ing Points of Fats and other Compounds,” by F. Riidorff. The 
author points out the untrustworthiness of observations of melt- 
ing points made, as they often are, by heating the substance to 
be examined in a capillary tube, or by coating the bulb of the 
thermometer with it. He recommends the observation of the 
freezing point, witha thermometer whose bulb is actually immers.d 
in the substance, as a means cf establishing its chemical identity 
instead of observing the melting point. Toascertain whether the ob- 
served temperature is the highest at which solidification can occur, 
he notices whether it is accompanied by rise of temperature, which 
always takes place if the body has been cooled below the normal 
freezing point. (7.) ‘‘ Onthe Phosphorescence of Rarefied Gases 
after the passage of an Electric Discharge,” by E. Sarasin. The 
author finds that the presence of oxygen, either free, or combined 
in a compound which is probably decomposed by the discharge, 
is an essential condition 1f the occurrence of the phosphorescence, 
and shows that this phenomenon is probably connected with 
the formation of ozone. Sulphuric acid vapour favours the 
production of phosphorescence in a high degree. (8.) ‘On 
the Electromotive Forces due to the contact of different metals,” 
by E. Edlund. When an electric current traverses the point 
of junction of two different metals, a quantity of heat is 
absorbed or produced per unit of time which is proportional 
to the strength of the current and to the electromotive force 
acting between the metals. The author refers on this point 
to a previous paper (Poggendoft’s Annalen, vol. XXXVI.) ; in 
the present communication he endeavours to estimate the 
comparative electromotive torces acting between different pairs of 
