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1. Caventou on the Chemical Properties of Starch, and the 

 various Amylaceous Substances of Commerce. % Ei^gel- 

 HART on the Colouring Principle of the Blood. S. On Arsenic^ 

 its Oxides, and Sulphur ets ; hy M. Guibourt. 4. Pre- 

 paration of Chloride of Lime. 5. On tJie Detection of Ar- 

 senic. 6, On Cqfeine. 7. Analysis of the Root of the Bryonia 

 alba. 8. General Treussart on the Preparation of HydraU" 

 lie Cements. 9- On a New Method of Purifying Crystals ; 

 by M. RoBiNET. 10. Repetition of the Comparison of the 

 Rate of the Mercurial and Spirit Thermometer. 



1. Caventou on the Chemical Properties of Starch, and the 

 various Amylaceous Substances found in Commerce. 



xN order to determine the relative nature of the different kinds 

 of amylaceous substances, such as Salep, Sago, Tapioca, and 

 Arrow-root, M. Caventou found it necessary to revise the chemi- 

 cal examination of pure fecula or starch ; and the result is, that, 

 besides adding some interesting facts on the chemical properties 

 of that principle, he has been able to account satisfactorily for the 

 differences which it exhibits in its various natural states. 



Chemists, he says, have too generally considered the action of 

 warm-water on starch as one of simple solution or gelatinization, 

 although they are perfectly aware that its properties are mate- 

 rially changed. In its unmodified state, it is insoluble in cold 

 water; but water at a temperature between 140° and 160° Fahr. 

 converts it into a transparent gelatinous mass, which is common- 

 ly regarded as a hydrate of fecula. It is essentially different 

 from the true hydrates, however, because its former properties 

 cannot be restored by the abstraction of the water ; and in par- 

 ticular, it is rendered more or less soluble in that fluid, and can- 

 not in any way recover its insolubility. This change is the 

 effect of heat ; for it may be equally brought about by expo- 

 sing dry starch to heat ; but in that case a higher tempera- 

 ture is required, namely, a Httle above 212°, or under the point 

 at which decomposition takes place. It then acquires a red* 

 dish colour, smells like baked bread, and forms with cold water 

 a paste just like that procured at once in the humid way, by 



