The exact relationship of the tetracetate to the original cellulose is somewhat difficult to determine. The starting-point is a cellulose hydrate, since it is the product obtained by decomposition of the sulphocarbonate. The degree of _hydrolysis_ attending the cycle of reactions is indicated by the formula 4 C_{6}H_{10}O_{5}.H_{2}O. It has been already shown that this degree of hydrolysis does not produce molecular disaggregation. If this hydrate survived the acetylation it would of course affect the empirical composition, i.e. chiefly the carbon percentage, of the product. It may be here pointed out that the extreme variation of the carbon in this group of carbohydrate esters is as between C_{14}H_{20}O_{10} (C = 48.3 p.ct.) and C_{14}H_{18}O_{9} (C = 50.8 p.ct.) i.e. a tetracetate of C_{6}H_{12}O_{6} and C_{6}H_{10}O_{5} respectively. In the fractional intermediate terms it is clear that we come within the range of ordinary experimental errors, and to solve this critical point by way of ultimate analysis must involve an extended series of analyses with precautions for specially minimising and quantifying the error. The determination of the acetyl by saponification is also subject to an error sufficiently large to preclude the results being applied to solve the point. While, therefore, we must defer the final statement as to whether the tetracetate is produced from or contains a partly hydrolysed cellulose molecule, it is clear that at least a large proportion of the unit groups must be acetylated in the proportion C_{6}H_{6}O.(OAc)_{4}. It has been shown that by the method of Franchimont a higher proportion of acetyl groups can be introduced; but this result involves a destructive hydrolysis of the cellulose: the acetates are not derivatives of cellulose, but of products of hydrolytic decomposition. It appears, therefore, that with the normal limit of acetylation at the tetracetate the aggregation of the unit groups must depend upon the CO- groups and a ring formula of the general form CO<[CHOH]_{4}>CH_{2} is consistent with the facts. Vignon has proposed for cellulose the constitutional formula O------CH | | \ | O \[CHOH]_{3} | | / CH_{2}-CH/