The central compound of the carbohydrates is glucose and it is around this substance that the chemistry of the carbohydrates and their molecular structure has been developed. The empirical formula was early established as CH2O and on the development of the Beckmann Apparatus the true formula was shown to be C₆H₁₂O₆ by Tollens and Mayer. Meanwhile, Killani (1886) had demonstrated the presence of an aldehyde group by forming the cyanhydrin, which on hydrolysis and reduction gave n-heptoic acid. The formation of this acid also indicated that the six carbons were arranged in a straight chain. The next major development was the introduction by Fischer of the “Fischer Projection Formula”. This structure with four asymmetric carbon atoms and hence allowing for 24 or 16 optical isomers (Vant Hoff – Le Bel Theory,) accounted for the numerous optical isomers of glucose that were being reported at the time, e.g. galactose by Pasteur as early as 1856.