328 Dr. G. ^mVs Observations on some of the Products 



these were separated and drained on filtering paper : on be- 

 ing subsequently examined, they also proved to be oxalic 

 acid like the first formed crystals, from which they altogether 

 differed in their physical characters. I am quite unable to 

 account for the curious forms assumed by the second crop of 

 oxalic acid crystals ; not having submitted them to analysis 

 1 cannot state whether they contained the same quantity of 

 water of crystallization as those possessing the ordinary cry- 

 stalline form. 



Having thus shown that oxalic acid is not a constant pro- 

 duct during the preparation of nitrous aether, at least in the 

 earlier stages of the operation, I was anxious to ascertain 

 whether the evolution of aldehyd and formation of oxalic 

 acid bore anything like a mutual relation. For this purpose 

 the following experiment was performed. A quantity of the 

 fluid left in the retort after the preparation of sp. aeth. nitrici 

 was placed in a tubulated retort, and a quilled receiver was 

 so adapted as to allow a receiving bottle placed beneath to 

 be changed and removed at will. A sand-heat was then ap- 

 plied and distillation commenced : when about one fourth of 

 the fluid had passed over, the receiving bottle was charged 

 and the fluid examined; it was colourless, aromatic, of sp. gr. 

 0'861, was unaffected or nearly so by the addition of alkaline 

 solutions, and appeared to be merely an alcoholic solution of 

 hvponitrous aether which had not been completely removed 

 by the operation on the large scale. Some of the fluid in the 

 retort was removed and examined ; it was nearly totally free 

 from oxalic acid, and appeared to contain among new pro- 

 ducts only the oxal-hydric acid. Heat was again applied to 

 the retort, and about a third of the remaining fluid was di- 

 stilled over; this was of sp. gr. 0872, exceedingly acrid, like 

 capsicum in flavour, acid, and assumed a deep orange tint by 

 the addition of solution of potass even in the cold ; this in- 

 creased by heat, and the subsequent addition of dilute sul- 

 phuric acid produced a copious deposition of the resin of 

 aldehyd. The fluid in the retort contained a large quantity 

 of oxalic acid, formed probably by the reaction of the free 

 nitric acid present upon the oxal-hydric acid formed in the 

 first stage of the operation. Upon a third application of 

 heat distillation was carried on until red fumes appeared; the 

 fluid in the receiving bottle was of sp. gr, 0*972, very acid, 

 scarcely contained any aether, and much less aldehyd than 

 the portion previously distilled, as it was merely tinged yel- 

 low by potass : the fluid left in the retort was so loaded with 

 oxalic acid that it crystallized by cooling. 



From these experiments, one fact at least of pharmaceutical 



