CHEMISTRY. 



91 



ence of an adulterating material ; but the pro- 

 cess is rather long and delicate. Dr. Phipson 

 has shown, in a note on the "Absorption 

 Spectra yielded by Certain Organic Substan- 

 ces," that the pure coloring matter of the 

 grape gives no absorption bands, but only a 

 general absorption, increasing gradually toward 

 the violet; while the coloring matter of the 

 purple holyoak, dissolved in water containing a 

 little alum, gives a distinct and wide absorption 

 band. This allows its presence in wine to be 

 detected without much difficulty; and the 

 same method applies equally well to the color- 

 ing matters of logwood and Brazil-wood. He 

 has not yet ascertained how the coloring mat- 

 ter of elderberry-fruit affects the spectrum, but 

 it is not difficult to discover in wine, according 

 to M. Faure, by means of gelatine. The fact 

 is that cenocyanine is easily precipitated along 

 with the tannin when gelatine is added to red 

 wine, while other coloring matters (and, 

 among them, that of the elderberry) are left 

 in solution. If there happen to be not enough 

 tannin naturally present in the liquid to pre- 

 cipitate all the oenocyanine, a little more must 

 be added. Alum will be often found in wine 

 which is artificially colored ; it vivifies the tint, 

 and is supposed to preserve the wine. Its 

 presence is not only highly injurious to the 

 health, but will effectually prevent the ripen- 

 ing of wine and the development of the bou- 

 quet. The test to which the author has called 

 attention may be made as follows: Take a 

 specimen of the wine to be examined, and, if 

 its color is too powerful when examined in a 

 thin tube by means of the prism, it must be 

 diluted with distilled water until a proper de- 

 gree of transparency is obtained. A minute 

 quantity of alum is then added, and the speci- 

 men examined in the spectroscope. If an ab- 

 sorption band of any kind shows itself, the 

 wine may be suspected. 



Lowering of Temperatures in Saline Solu- 

 tions. Experiments, conducted by Rudorff, 

 yield much valuable information with regard 

 to the lowering of temperature by the solution 

 of salts in water. It is well known that the 

 decrease of temperature will be the greater, 

 the larger the quantity of any salt which water 

 takes up at a certain temperature. Since, 

 however, water at a certain temperature only 

 dissolves a definite quantity of any salt, the 

 maximum decrease will be about that at which, 

 under given circumstances, a fully-saturated 

 solution is produced. To conduct the experi- 

 ments successfully, the saturated solution should 

 be obtained as rapidly as possible. Rudorff 

 proceeded in the following manner : The finely- 

 powdered salt and the requisite quantities of 

 water were, previous to the making of the ex- 

 periments, each put in separate beakers made 

 of very thin glass, and placed for from twelve 

 to eighteen hours in a room wherein the tem- 

 perature could be kept as nearly as possible 

 constant. In consequence of this, the beakers 

 and contents attained th same temperature 



throughout. The mixing was effected by pour- 

 ing the water on to the salt, and stirring up 

 with a very delicate and highly-sensitive ther- 

 mometer; the maximum decrease of temper- 

 ature took place within a minute after the 

 mixing of the salt and water was made. The 

 results of the experiments are exhibited in the 

 following tabulated form, recording the aver- 

 age of a series of several experiments with one 

 and the same substance, which were concord- 

 ant within 0.2 : 



used corresponded therewith. The decrease 

 of temperature obtainable in this manner can 

 never fall below the freezing-point of the 

 saline solution in question, but can very nearly 

 reach that. The Sulphocyanide of potassium 

 is the best salt to be adopted for the artificial 

 production of ice : when 500 grammes of this 

 salt are dissolved in 400 cubic centimetres of 

 water, and the mixture stirred with a test-tube 

 filled with water, the latter will be frozen in 

 from two to three minutes. The degree of 

 solubility of the salts referred to in the first 

 column is made up according to G. J. Mulder's 

 highly-elaborate researches on this subject. 



Recovery of /Sulphur from Alkali Waste. 

 Mr. Ludwig Mond read a paper on this sub- 

 ject at a session of the Newcastle Chemical 

 Society, in May. The following is the sub- 

 stance of his statements: He said that in 

 1860 he commenced, in a chemical manufactory 

 in Germany, a series of experiments on several 

 processes for the recovery of sulphur from 

 waste, and took out a patent in 1861. When 

 he came to England ( at the time of the Exhi- 

 bition) he found, to his surprise, that a pro- 

 cess, somewhat resembling his own, had been 

 proposed as early as 1836. At the same time 

 as himself, three different parties in Glasgow, 

 in Newcastle, and in Bristol had been work- 



