— 189 — 



The drawback which has now been exposed is of less 

 importance, because, by means of a simple method, the 

 decrease in the dry-residue can, if so desired, be practically 

 almost if not entirely avoided. For this purpose a sample 

 of the rice which is to undergo investigation is kept in 

 the vapour of formaldehyde, chloroform or carbon tetra- 

 chloride. Of these substances it seems up till now that 

 formaline is best able to counteract the instability; experi- 

 ments in this direction are however being continued, in order 

 to find out which of these substances really deserves the 

 preference for the aim mentioned. 



All the above-named objections are in reality only in so 

 far to the disadvantage of the test by spirit that thereby 

 the difficulty is increased of determining the limit which 

 ought to be fixed for the dry-residue, in order to judge as 

 the sufficiency or insufficiency of a certain kind of rice for 

 giving protection against beri-beri. 



This difficulty already exists from other reasons. For 

 instance, various differences which had formerly appeared 

 between the proportion of the P 2 5 content and the activity 

 of the rice, evidently existed, and in still greater measure, 

 with regard to the relation of the spirit dry-residue and the 

 degree of activity. 



Another source of inaccuracy connected with the spirit 

 cipher is found to lie in the investigation itself, in so far 

 that hereby a certain weigt of rice grains was taken as 

 basis and not a certain surface of grains — which really 

 would be necessary for a more correct relative comparison 

 of results. It stands to reason that a certain quantity of 

 rice with smaller grains offers a larger surface for extraction 

 by spirit and will therefore show a higher relative proportion 

 of dry-residue than is the case with the same quantity of 

 larger grains. Even for this reason alone, from the point 

 of view of chemical accuracy, the test deserves condem- 

 nation. All the same, it is practically impossible to make the 

 experiment with a certain surface of grains as point of departure. 



