:PoLTTEcnNic Association Proceedings. 575' 



during those days. The same quantities of carbonic anhydride are 

 exhaled during the nights followirig days of work and inactivity, 

 and evidently result from the muscular movements made during 

 sleep; but on the nights following working days there is a great 

 increase in water given ofl" by respiration and perspiration. The 

 same amount of urea is secreted in working as in resting da3^s, 

 showing that the work of the muscles is performed without an 

 increase in the decomposition of albuminoid substances. Tliis 

 statement does not agree with the experiments made by Houghton 

 as to the quantity of urea resulting from muscular or mental work. 

 The general results obtained by the first named experimenters con- 

 firm those by Heuneberg in 1861, when experimenting on oxen. 



ALUMINIUSI ALLOY IN DENTISTRY. 



A process for casting an aluminium alloy has been invented, 

 which will furnish a very light foundation for artificial teeth, not 

 aflected, like gold, by sulphur compounds. 



A NEW PHOTOMETEK. 



Prof. Schonbeiu uses a solution of cyanin as a photometer. He 

 finds the depth of color which it takes on exposure to light varies 

 in proportion to the intensity of light, and that the phenomenon 

 occurs also in vacuo. Cyanin is the coloring matter of certain 

 flowers. It is contained in the blue petals of corn-flowers, violets 

 and several species of iris. Marquart states that it is found in red 

 and black, as well as blue flowers. It is extracted by means of 

 alcohol. On evaporation to dryness the residue is treated with 

 water to separate a resinous substance and dissolve the coloring 

 matter, which is precipitated by means of the acetate of lead 

 {plvbmealort). The green precipitate, after being treated with 

 water, is decomposed by sulphuretted hydrogen {gelas). After 

 carefully evaporating the filtrate over a water bath, the residue is 

 treated with absolute alcohol; lastly, the alcoholic solution is 

 mixed with ether, which precipitates the cyanin in blue flocks. 

 C}\inin, as thus prepared by Fremy k Cloez, is an uncrystalizable 

 mass, which is decolorized by reducing agents, but it recovers its 

 blue color on exposure to air. It has been supposed that red 

 flowers owe their color to cyanin reddened by a free acid, which 

 may account for the fact that certain flowers are red in the bud, 

 blue in the blossom, and green when they begin to fade. Schon- 

 bein's photometer, like all others, depends for accuracy upon a 

 correct estimate of tint by the human eye. 



