96 NUTRITIVE PLANTS. 



of alcohol into syrup of starch. The precipitate first formed was 

 composed of sulphat of lime and gum. When this was separated, 

 he poured more alcohol into the syrup that had been decanted from 

 it. The second precipitate was gummy matter, unmixed with sul- 

 phate : its solution in water was no longer rendered turbid by mu- 

 riat of barytes. 



The author, however, was not content with this experiment ; for 

 it might be objected to him, that the sulphuric acid being chemi- 

 cally combined with the gum, would not quit it to unite with the 

 barytes. He dissolved this gum therefore in barytes water evapo- 

 rated to dryness, and gave the mass a strong red heat in a platina 

 crucible : thus the sulphuric acid should have been set free, and 

 no doubt would have seized on the barytes. Besides, this sulphat 

 would have been decomposed by the carbon of the gum, and con- 

 verted into a sulphuret : but muriatic acid poured on the calcined 

 matter extricated nothing but carbonic acid gas, and not an atom of 

 sulphuretted hydrogen gas that could be rendered sensible by paper 

 impregnated with acetate of lead. 



Besides, the gum distilled on an open fire did not give out any 

 sulphureous acid, or sulphuretted hydrogen gas. 



It is not therefore a hydrat of starch combined with sulphuric 

 acid ; which affords us a fresh proof that we must take care not to 

 frame hypotheses before we consult experiment. 



He made the same trials with the syrup deprived of gum by 

 alcohol, which did not precipitate the muriat of barytes ; but he 

 could not discover in it the least trace of combined sulphuric acid. 



These experiments could not fail gradually to lead to an exami- 

 nation of the action of acids diluted with water on some other sub- 

 stances. Sugar of milk first drew his attention; and with the 

 greater reason, as this substance becomes more soluble in water, 

 after it has been treated with acid. 



M. Vogel boiled 100 gr. (1545 grs.) of sugar of milk with 400 gr. 

 of water, and 2 gr. of sulphuric acid at 56 (1.631), for three hours, 

 adding more water as it evaporated. After having saturated the 

 excess of acid by carbonat of lime, he filtered. 



The liquid, though clear, was slightly coloured. Evaporated 

 slowly in a stove, a thick brownish syrup remained, which con- 

 creted into a crystalline mass at the expiration of a few days. 



This matter resembling soft sugar has a much more saccharine 



