538 



sequence of the lead salts forming such gelatinous precipitates, they 

 could not be employed for determining the equivalent of datiscine. 



Action of dilute Sulphuric Acid on Datiscine. When an aqueous 

 solution of datiscine is boiled for a few minutes with very dilute sul- 

 phuric acid, it deposits a crystalline substance. On examining the 

 solution filtered from the crystals, very distinct evidences of the 

 presence of sugar were obtained. These experiments show there- 

 fore that datiscine, like salicine and similar bodies, belongs to the 

 class of glucosides, and is a copulated compound of sugar and 

 another substance which I shall call " datiscetine." 



Datiscetine. Datiscetine in its general appearance and pro- 

 perties closely resembles datiscine, but on a closer examination 

 these two substances are found to differ essentially both in com- 

 position and properties. Datiscetine when pure assumes the form 

 of fine needles which are nearly colourless. It is easily soluble in 

 alcohol, a hot alcoholic solution, on cooling, depositing the greater 

 portion in crystalline groups. It is almost insoluble in water, con- 

 sequently datiscetine is precipitated from its alcoholic solutions by 

 the addition of water. It dissolves in ether in almost any quantity, 

 and is deposited on the evaporation of that liquid in needles. These 

 properties of datiscetine enable us to obtain it in a tolerably pure 

 state, even when very impure datiscine is employed in its pre- 

 paration. 



Properties of Datiscetine. Datiscetine has no taste. When 

 heated it melts like datiscine, but the heat required is much higher 

 than for that body. It recrystallizes on cooling. By operating very 

 cautiously, a portion of the datiscetine may be sublimed. The sub- 

 limate, however, appears to be altered datiscetine. Datiscetine 

 when burned does not emit the odour of caramel. Datiscetine, 

 like datiscine, dissolves in alkaline solutions, and is reprecipitated 

 by the addition of an acid. An alcoholic solution of acetate of lead 

 added to an alcoholic solution of datiscetine produces a deep yellow 

 precipitate, which can be easily washed both by alcohol and water. 

 This precipitate therefore was subjected to analysis, and from the 

 results obtained, the formula C <30 H g O 10 + 2PbO was calculated, 

 which agrees with the formula (C 30 H 10 O 12 ) derived from tlie 

 analysis of datiscetine. 



Analysis of Datiscine. It is difficult to calculate a formula for 



