166 On the preparation of Opium for the China market. [March, 



vacuo is incomparably the most efficient in preserving unaltered the 

 original taste of the sugar, and the taste, solubility, and therapeutic 

 powers of the extracts. It is also known that this process owes its 

 superiority to the exclusion of the chemical as well as the physical 

 agency of the atmosphere, to its rapidity of exsiccation, and to the 

 comparative lowness of temperature at which it is performed. When 

 sugar-cane juice, after even half an hour's exposure to the air, is boiled 

 in a narrow deep vessel, and under the pressure of the atmosphere, 

 vaporisation goes on so slowly that the sugar has time to undergo the 

 vinous and acetous fermentations, whereby a certain portion of it is 

 converted into vinegar, before the heat can be raised high enough to 

 check this change ; and the high temperature, to which it is so long 

 exposed during this slow vaporisation, chars another portion, and 

 converts it into molasses. Other vegetable juices, under similar cir- 

 cumstances, undergo analogous transformations : much of their sub- 

 stance is converted into vinegar ; and the high temperature causes a 

 partial decomposition of the rest : oxygen also is largely absorbed 

 from the atmosphere, and greatly impairs the solubility of the dried 

 extract. 



6. On the principles which flow from these facts, it would be, chemi- 

 cally speaking, advisable to prepare opium by distilling in vacuo, large 

 quantities of the milk just as it has oozed from the capsules ; and I 

 have no doubt that opium thus prepared would possess in an unprece- 

 dented degree the desired qualities of solubility and strength, and 

 purity of flavour, as well as narcotic power ; and can imagine, that 

 under a system of open trade in opium, this process would be commer- 

 cially profitable. It would, however, be inapplicable under a mono- 

 poly constituted as the present system is ; and I have mentioned it 

 only with the view of pointing it out as the acme of that perfection in 

 the preparation of vegetable juices to which we can, with our present 

 means, only approximate. 



7. That the approximation may proceed as far as possible, it will 

 be necessary, first, that the poppy juice shall at the time of collection, 

 contain a minimum of water ; so that its reduction to the proposed 

 degree of spissitude may be effected in the shortest time, and be there- 

 fore attended with the least exposure to the air at a high temperature, 

 and with the smallest consequent loss of solubility and of specific qua- 

 lities that may be practicable. 



8. The goodness of the soil, and the management of the irrigation, 

 are circumstances which powerfully affect the strength of the juice at 

 the time of its collection : but a third agent, still less amenable than 

 these to control, now comes into play, the precipitation of dew on the 



