96 Mr W. Gardiner, On the constitution [Feb. 11, 



from Fre'my's paper, the paracellulose forms in great part the 

 substance of the cuticularised layers of the epidermis, and since, 

 as we saw, it is also met with in other tissues, one must conclude 

 that this form of cellulose is of more general occurrence than has 

 hitherto been imagined. Some interest also is attached to that 

 particular form which turns blue with iodine alone. It has been 

 long known that after the action of such acids as sulphuric, phos- 

 phoric, or iodic acids, cellulose walls will give a blue instead of a 

 yellow, with iodine. In enquiring into the meaning of this phe- 

 nomenon, we receive great assistance from the many investigations 

 made under the directions of Prof. DragendorfT, which have special 

 reference to the constitution of pure cellulose. 



Although the formula of cellulose is usually regarded as C e H 10 O s , 

 Stackmann 1 found that an analysis of the cellulose of conifer- wood 

 gave for the formula 5 (C 6 H 10 O s ) + H 2 0. These results agreed with 

 those of Koroll 2 on the constitution of the cellulose of sclerenchy- 

 matous and bast tissue. Similarly the cellulose of parenchyma 

 cells gave 5 (C 6 H 10 O 5 ) + 2H 2 0, while that from the wood of most 

 Dicotyledons gave 5 (C 6 H 10 O 5 ) + 3H 2 0. In all these analyses sul- 

 phuric acid was used in the purification. Schuppe 3 on the other 

 hand, working his purification in the absence of sulphuric acid, 

 found that the body thus separated was in all cases simply repre- 

 sented by C 6 H 10 O 5 . As a result of these experiments it would 

 then appear, that the use of sulphuric acid occasions a definite 

 hydration of the cellulose, in the same way as we know it does in 

 other chemical reactions 4 . 



Leaving for a moment the subject under immediate considera- 

 tion, we find that Nageli 5 and Sachsse 6 , in their analysis of starch, 

 found that the body should not be represented by C 6 H 10 O 5 , but 

 that the constitution expressed by the formula 6 C 6 H 10 O 5 + H 2 

 was much more exact. Then comparing together, the facts with 

 regard to the composition of starch, and of cellulose, it appears 

 in the light of Schuppe's results, that the action of sulphuric acid 

 and the like, brings about a definite hydration, in consequence of 

 which a hydrated cellulose is produced, which, though it is most 

 probably not identical with starch, yet approaches it in its con- 

 stitution and, what is more, gives a blue colour with iodine. The 

 cellulose met with in the asci of Lichens — (the so called Lichen- 



1 Stackmann, Studien iiber die Zusammensetzung d. Holzes. Diss. Dorpat, 

 1878. 



2 Koroll, Quant, chem. Unters. u. d. Zusammensetz. d. Kork-Bast, &c. Diss. 

 Dorpat, 1880. 



3 Schuppe, Beitrage z. Chemie d. Holzgewebes. Diss. Dorpat, 1882. 



4 The production of ethyl alcohol by the action of sulphuric acid on ethylene 

 is a case in point. 



5 Nageli, Annal. d. Chem. u. Pharm. clxxii. 218, 1874. 



6 Sachsse, Zeitschr. f. anal. Chem. xvn. 231, 1878. 



