440 PROFESSOR W. DITTMAR ON THE BEHAVIOUR OF THE 



find that even the caustic alkalies proper, if kept at a red heat in hydrogen, suffer at 

 least partial dehydration, and caused Mr Hodge to try some experiments with caustic 

 soda to test the presumption. These experiments, however, proved more difficult than I 

 had expected. There would have been no use in trying to dehydrate caustic soda at a 

 temperature below redness ; and at a red heat, besides volatilising pretty fast, it "creeps" 

 to an exasperating extent, so that after half an hour's heating (of some 2 to 3 grm. of 

 substance), the crucible, when opened, was found almost empty, and the little of a 

 residue that there was had to be scraped it before it could have been analysed, which it 

 was impossible to accomplish without the substance absorbing water from the atmosphere. 

 Mr Hodge analysed one or two of his products, but I did not preserve his numbers, because 

 they did not prove the presence of real Na 2 0, and, in the circumstances, could not be 

 taken as proving the absence of this component in the real product. 



Not feeling inclined to lose any more time over the matter, I simply left it on one 

 side; but I subsequently found that the creeping of the fused alkali can be effectually 

 prevented by burying it in a sufficiency of spongy platinum. A circular piece of platinum 

 foil is turned into the shape of a cornet, whose seam is made fast and approximately 

 tight by welding. The cornet is filled to about half its height with spongy platinum, 

 the alkali put on the top and then covered over with more spongy metal so as to fill the 

 cornet. The charged cornet is placed in the gas crucible and heated in the desired 

 atmosphere. At the end of the experiment it is taken out, while still warm, with a 

 forceps, quickly transferred to a wide weighing-tube provided with a hollow ground-in 

 stopper, and weighed. For the determination of the carbonic acid and base it is placed 

 in the decomposition-flask as it is. As the spongy metal forms a coherent mass, it is 

 easy, at the end, to lift out the cornet and spongy metal, dry, ignite, and weigh it. I 

 never came to use this method in connection with the hydrates, but I subsequently 

 applied it occasionally in my experiments on the carbonates of the alkalies, and it is 

 for this reason that I have here described it. 



Experiments with Carbonates. 



As early as 1860, Theodor Scheerer,* in the course of an investigation on the 

 behaviour of silica to the carbonates of potash and of soda at certain approximately con- 

 stant temperatures situated above their fusing-points, inquired into the behaviour of the 

 unmixed carbonates under the same circumstances, and as a general result found that 

 both reagents, when kept in a state of fusion within a well-covered platinum crucible, 

 lost weight, the more largely the higher the temperature. The source of heat in all 

 cases was a Berzelius spirit-lamp, i.e., a spirit-lamp constructed on the Argand principle. 

 To produce " Rothyluth" the lamp was fed with spirit of 66° to 70° Richter; a 

 somewhat higher temperature, "Orangegluth," was established by using 80° to 81° spirit, 

 and keeping the level of the spirit constant. For the production of " Gelbgluth" the 

 same lamp (and the stronger spirit) was used in conjunction with the blast arrangement 



* Likbig's Annalen, vol. cxvi. page 129. 



