406 Comparative ^rialyfes of Gums and Sugar. 



VI. 



Experiments and Obfervations on the Nature of Sugar, and of Vegetalle Mu'cUiige. By Mr, 

 William CruickSHANK, Chemijl to t^e Ordnance, ^c* 



F 



ROM the failure of thefe trials to convert mucilages into fomething refembling fugar, 

 we began to fufpe£l that they were not fo fimple as had been generally fuppofed. With a 

 view to throw fome light on this fubjeft, the following comparative experiments were made : 



One ounce of powdered gum arable was introduced into a coated glafs retort, to which a 

 receiver with the pneumato-chemical apparatus was adapted : heat being gradually applied, 

 there came over into the receiver 3 dr. 30 gr. of pyromucous acid, mixed with a little heavy 

 empyfeumntic oil. After the retort had been red-hot for fome time, it was removed, and the 

 charry refiduum which it contained was found to weigh i dr. 46 gr. This had a greyifh co- 

 lour, and burned very flov/Iy ; but when expofed to a flrong heat in an open crucible, is 

 left a whitifli powder, amounting to i o grains, which was found to be lime tnixed with a 

 very fmnll' proportion of calcareous phofphate. 



The pyromucous acid being fuper-faturated with Hme, a ftrong fmell of ammonia was 

 inftantly perceived ; and a piece of paper dipped in muriatic acid being held over the veflel, 

 copious white fumes were immediately produced. This circumftance fhews, that azote 

 forms a conftituent part of the gum. 



There were collefted in the pneumato-chemical apparatus 273 oz. meafures of gas; of 

 this 93 were carbonic acid, and the remaining 180, that fpecies of hydro- carbonate which 

 is obtained by heat from moiflened charcoal. 



Two meafures of this gas, well freed from carbonic aci-d, were mixed with i^- of very 

 pure oxygen gas, and introduced in a ftrong glafs jar, filled with and inverted over mer- 

 cury : when fired by the eleftric fliock, they occupied the fpace of one meafure only r 

 lime water being admitted, the whole was ablorbed, except a very fmall particle, which was 

 found, from the nitrous teft, to be pure air. From a number of experiments we have 

 found, that twelve meafures of oxygen gas, when united with carbon, produce ten of 

 carbonic acid gas. Hence it fbllows, that the quantity of oxygen gas neceflary to the for- 

 mation of carbonic acid gas muft, in this tafe, have been i.i. meafures, or a little better ; 

 the remaining 4 muft therefore have been confumed in the production of water, and would 

 be fufficient to faturate .8 of hydrogen, equal in weight to .048 of a grain nearly. 



• Thefe Experiments, &c. area continuation of the Refearch communicated in the' firft volume of this 

 Journal, page a-^. In the fecond edition of Dr. Rollo's Treatife on Diabetes Mellitus in which that article 

 is reprinted, and whence the above is taken, there are a few emendations in the fecond and third parar 

 graphs, as follow : The fiigar afforded £^ drams of acid, which required 1 50 grains of the alkalme foiution to 

 faturate it; the charry refidue was 5 drams; and the gas. which ^fcaped li drams. The gum arabic afforded 

 7 dr. 40 gr. of acid, which required 118 grains of the fob:tion of pot-afli to faturate it ; t!;e charry refidue 

 ■was 3 dr. 45 gr.j and the gas which efcapcd 5 drams. Whence the fugar yielded more pyromucous acid than- 

 the gum, in the proportion of 150 to iig. 



The concluding paragraph on page 341, beginning, " InJefd, -when ive reJleB," &c. is cancelled, and the 

 inveftigation is continued as in the text. The prefent article mtlft therefore be read as a continuation from 

 vol. L p. 341, of this Journal.. N., 



