508 Prof. G. Gulliver on Raphides. 



XLIX. — Observations on Raphides. 

 By Geokge Gulliver, F.R.S. 



[Continued from p. 409.] 



Their Chemical Composition, — Since the observations of Ras- 

 pail and Edwin Quekett, raphides have generally been regarded 

 as composed of phosphate of lime, and many sphseraphides as 

 oxalate of that earth. But, in the 'Trans. Edin. Bot. Soc.^ for 

 1861, Prof. Douglas Maclagan gave an analysis of the raphides 

 of Richardia, from which it results that these are composed of 

 the oxalate. Hence further observations seemed so desirable on 

 the subject, that Dr. Davy kindly undertook, at my request, the 

 examination of several specimens which I sent to him ; and, with 

 his permission, the following notes of his experiments are here 

 published : — 



" Owing to the minute quantity of matter in the raphides or 

 other crystals (minute even in relation to the quantity of ash 

 afforded by the leaf or other vegetable structure), there is diffi- 

 culty in coming to more than a proximate conclusion as to their 

 composition. It is not improbable that, in some instances, it 

 is composite, consisting, for example, of oxalate of lime and 

 magnesia. Possibly vegetable matter may influence the reagents. 

 In the scales of the onion, I found the precipitate from an acid 

 solution, by ammonia in excess, in the form only of minute 

 well-defined crystalline globules. Raphides may generally con- 

 tain a little vegetable matter, in consequence of which their 

 forms, though somewhat altered, remain after the matter which 

 is soluble in an acid (such as phosphate of lime), or is in part 

 fixed after combustion (such as the lime of the oxalate), is re- 

 moved. 



" 1. Officinal Iris Florentina contains a good deal of lime. Its 

 white ash consists chiefly of lime, and, strongly heated, emits a 

 brilliant white light. The ash contains a small proportion of 

 phosphate of lime, but a much larger of carbonate. From the 

 crystals resisting the action of dilute acetic acid, I infer that 

 they are of oxalate of lime. They are rapidly dissolved by strong 

 nitric acid, and some by acetic acid, without effervescence. 



*' 2. Mesembryanthemum muricatum is readily incinerated (the 

 leaves more readily than the stalk) ; it yields a good deal of 

 white ash, retaining the form of the leaf, but shrunken. Ignited, 

 it shines with a bright yellow light, that of the stalk with a red 

 light. The raphides, I infer, are composed chiefly of oxalate of 

 lime and magnesia, with perhaps a little silica, the magnesia in 

 rather larger proportion than the lime. They are not dissolved in 

 dilute acetic acid. The leaves, under the action of dilute muriatic 

 acid, give up the greater portion of their saline and earthy 



