TEANSACTIONS OF THE SECTIONS. 59 



of producing, but molecules like those found in a leaf or in tlie stem of a tree 

 ■will no doubt one day be manufactured from their elements. 



I must not conclude this address without reference to two or three papers of 

 great importance. 



Professor Buusen, of Heidelberg, has published a paper on the washing of pre- 

 cipitates. Every one acquainted with practical chemistry knows how much time 

 is often lost in waiting for a liquid to pass through a filter. Bunsen found the 

 rate of filtration nearly proportional to the difference between the pressures on the 

 upper and lower surfaces of the liquid. If, accordingly, the funnel be fixed air- 

 tight by means of a perforated cork to the neck of a bottle, and the air exhausted 

 in the bottle, the liquid will run faster through the filter in proportion to the di- 

 minution of the pressure in the bottle. Comparative experiments, some made 

 according to the old, and others accordiug to the new method, showed that the fil- 

 tration, washing, and drying of a precipitate which took seven hours by the old 

 plan could be performed by filtration into an exhausted bottle in thirteen minutes, 

 but a saving of time is not the only advantage of the improved method of collect- 

 ing and washing precipitates. A more perfect washing with less water thau is re- 

 quired by the common way of proceeding is by no means the least recommenda- 

 tion of Bunsen's ingenious method. 



A very important paper has been published by Professor Liebig on the improve- 

 ment of the nomishing qualities of bread. Certain quantities of phosphates and 

 other salts form necessaiy ingredients of wholesome food. Xow, it is well known 

 that most of these salts, which are naturally in wheat, remain with the husk. 

 Liebig proposes to add salts, of a natiu-e similar to those remaining iu the husk, to' 

 the flour, and at the same time to substitute for the carbonic acid developed by fer- 

 mentation, gas liberated from sodic carbonate. The bread prepared accordiug to 

 Liebig's recommendation is said to be of excellent quality, and to exceed in value 

 bread made by the ordinary method. 



Mr. Graham, of Her Majesty's Mint, has continued his researches on the ab- 

 sorption of hydi-ogen by palladium. Palladium appears to be able to absorb more 

 than 900 times its volume of hydrogen, and to form a combination which consists 

 of nearly equal equivalents of the two elements. Hydrogenium, as Mr. Graham 

 calls the combined hydrogen, acts in this case like a metal, and thus the opinion held 

 by some scientific men, that hydrogen constitutes the vapour of a metal, receives 

 confirmation. The specific gravity of hydrogenium, as contained in the alloy, 

 was found to be 1'95. These experiments are remarkable in more than one re- 

 spect. The palladium, which absorbs and combines with the hydrogen, does not 

 change its state of aggregation, but remains solid and expands "as if it had been 

 heated. The molecules of the palladium have consequently changed their relative 

 positions and combined with hydrogen, whilst the continuity of the metal re- 

 mained intact. 



The last paper to which I have to draw your attention is an excellent one 

 by Professor Tyndall, on a new method of decomposing gaseous substances by 

 means of light. Tyndall's experiments bring us face to face with the motions of 

 atoms in molecides, and the relation of these motions to chemical decomposition. 

 They will no doubt, at some future time, furnish valuable materials to chemical 

 dynamics. 



On the Absorption-lands of Bile. By Thomas Andrews, M.B., F.R.S. 



A solution of bile in water or alcohol exhibits, when examined by the spec- 

 troscope, characteristic absorption-bands, which differ from those of the red colour- 

 ing-matter of blood or its derivatives. The most conspicuous of these bands lies 

 nearly midway between the yellow soidum-line and the green line 3 calcium. 

 Another band occurs, chiefly in the orange, extending a little beyond the sodium- 

 line. A third band occm-s in the green, bounded on its more refrangible side by 

 the magnesium group (J, Fraunhofer). These absorption-bands are also found in 

 solutions of bili\-erdin, but not in solutions of the yellow colouring-matter of bile. 

 They are not affected by reducing agents, but are weakened, and at last effaced by 

 the action of nitric acid. 



