Normal propyl alcohol 40.0 Normal butyl alcohol 218.6 Amyl alcohol 83.8 Hexyl alcohol 0.6 Heptyl alcohol 1.5 Ethyl acetate 35.0 Ethyl propionate, butyrate and caproate 3.0 Oenanthic ether (about) 4.0 Aldehyde 3.0 Acetal traces Amines traces
Most of the above substances, in fact probably all of them, excepting the oenanthic ether, are contained in other spirits, such as whisky and rum. The oenanthic ether (ethyl pelargonate) is one of the main characteristics which enable us chemically to differentiate between brandy and other distilled liquors. Brandy also contains a certain quantity of free acid, which increases with age, furfural, which decreases, and small quantities of other matters of which we have as yet little knowledge.
The table gives analyses, by the present author (excepting No. 3, which is by F. Lusson), of undoubtedly genuine commercial cognac brandies of various ages.
_Storage and Maturation._--Brandy is stored in specially selected oak casks, from which it extracts a certain quantity of colouring matter and tannin, &c. Commercial cognac brandies are generally blends of different growths and vintages, the blending being accomplished in large vats some little time prior to bottling. The necessary colouring and sweetening matter is added in the vat. In the case of pale brandies very little colouring and sweetening are added, the usual quantity being in the neighbourhood of ½ to 1%. Old "brown brandies," which are nowadays not in great demand, require more caramel and sugar than do the pale varieties. The preparation of the "liqueur," as the mixed caramel and sugar syrup is termed, is an operation requiring much experience, and the methods employed are kept strictly secret. Fine "liqueur" is prepared with high-class brandy, and is stored a number of years prior to use. Brandy, as is well known, improves very much with age (for chemical aspects of maturation see SPIRITS), but this only holds good when the spirit is in _wood_, for there is no material appreciation in quality after bottling. It is a mistake to believe, however, that brandy improves indefinitely, even when kept in wood, for, as a matter of fact, after a certain time--which varies considerably according to the type of brandy, the vintage, &c.--there is so much evaporation of alcohol that a number of undesirable changes come about. The brandy begins to "go back," and becomes, as it is called, "worn" or "tired." It is necessary, therefore, that the bottling should not be deferred too long. Sometimes, for trade reasons, it is necessary to keep brandy in cask for a long period, and under these conditions the practice is to keep a series of casks, which are treated as follows:--The last cask is kept filled by occasionally adding some spirit from the cask next in order, the latter is filled up by spirit taken from the third cask from the end, and so on, until the first cask in the row is reached. The latter is filled up or "topped" with some relatively fresh spirit.
