128 Mr. E. A. Parnell on the Composition of Inulin. 



24, Carbon 1 834-5 43'71 



21 Hydrogen .... 262-0 6-2.5 



21 Oxygen 2100-0 50-04 



1 Equivalent inulin 4-196-5 lOO'OO 



The analogy of this formula (the lowest whole numbers 

 which can be given) to gum, starch, grape and cane sugars, 

 will at once be apparent; each of these containing the mole- 

 cular group, 24 carbon, united to hydrogen and oxygen, in 

 the proportions to form water. But in the whole of these 

 (with one exception, the compound of chloride of barium and 

 cane sugar, lately examined by Peligot, C 24 H 21 O 21 + Ba Cl, 

 or C 24 H 18 O 18 + 3 H O, Ba Cl), the number of atoms ad- 

 mitting of division, the equivalent becomes doubtful. In 

 crystallized cane sugar, for instance, should the formula be 

 C 24 H 22 O 22 , or C 12 H u O n ? While in the case of inulin 

 this division is impossible. 



To satisfy myself as to the constitution of this substance, I 

 endeavoured to combine it with metallic oxides, but the only 

 one attended with success was oxide of lead. Neither ace- 

 tate nor subacetate of lead precipitates the aqueous solution 

 of inulin ; but on mixing its solution with the ammoniacal 

 acetate of lead, or on adding ammonia to the mixed solutions 

 of inulin and acetate of lead, a very bulky white precipitate 

 occurs, which is a hydrated inulate of lead. On heating and 

 stirring it partly dissolves, and the remainder aggregates to a 

 heavy tenacious mass, which also dissolves if sufficient water 

 be present. It is readily obtained pure by washing the pre- 

 cipitate as first produced in the cold with cold water, it being 

 impossible to wash clean after it has aggregated. But there 

 exist two of these inulates, possessing precisely the same 

 physical appearances, and only distinguishable by ultimate 

 analysis. I have procured both by the above process, and 

 have in vain sought for the peculiar circumstances of the for- 

 mation of each. Neither temperature, order of mixing the 

 ingredients, relative proportions, nor strength of solutions, 

 influences it in the slightest degree. The one most com- 

 monly formed possesses the composition C 24 H 21 O 21 + 5 PbO; 

 the other C 24 H 18 O 18 -t- 3 P b O, both being dried at 

 212. 



I may remark, that I have always obtained either one or 

 the other of these compounds, and never an indefinite mix- 

 ture of both. 



The mean of several analyses of one is, carbon 16-65, hy- 



