Ivi GENERAL SUMMARY OF SCIENTIEIC AND 



valerianat'CS, as well as the alcoholates. The author thinks these re- 

 sults are due to the formation of hydrates of the acid and the base 

 by the water added. In the first class the heat set free by the for- 

 mation of the hydrates is less, in the second greater, than is evolved 

 by the union of the acids and bases themselves. 



The same chemist has examined thermo-chemically the explosion 

 of gunpowder, in order to negative the view expressed by Noble and 

 Abel, that this phenomenon is incapable of exact chemical formula- 

 tion. He shows most clearly that when powder explodes there are 

 formed all the bodies which are stable in the conditions of the ex- 

 periment, principally potassium sulphide, sulphate, and carbonate, 

 as well as carbon dioxide, monoxide, nitrogen, and steam. The pro- 

 portions vary with the conditions of the experiments. These sub- 

 stances, if they remain in contact sufficiently long, suffer reciprocal 

 action which brings them to a single condition, i. e., that which cor- 

 responds to the maximum of heat set free. Each of these products 

 is formed according to a regular law nevertheless, and the chemical 

 transformations of the powder are expressed in all cases by a simul- 

 taneous system of very simple equations. 



Julius Thomsen has published a memoir on the heat of neutraliza- 

 tion of chemical substances, in which he gives the following conclu- 

 sions : the differences observed in the results obtained disappear if 

 the substances used be mixed in aqueous solution. The bases solu- 

 ble in water are thermally divided into two groups: First, that of 

 the hydrates, represented by potassium hydrate ; and, second, that of 

 the anhydrides, represented by ammonia, the typical heat of neutral- 

 ization being for the first group for one molecule of normal sulphate 

 31,300 calories, and for the second group 28,200 calories, at 18. For 

 the insoluble bases only the apjjarent heat of neutralization can be 

 measured, and this is the sura of the true neutralization heat and 

 that of solution of the base. If the former be the same for the bases 

 of the magnesia series (Mg, Mn, Fe, Ni, Co, Zn, Cu) as for the alkali 

 earths, the heat of solution of these bodies will be negative, that of 

 copper, for example, being 12,800 calories. 



The radiometer continues to be the subject of extensive experi- 

 mentation. Bottger, using a Geissler instrument, could not obtain 

 the slightest rotation with the full moon or with phosphorescent 

 tubes. A candle flame twenty-four centimeters distant, with an 

 alum plate interposed, gave a weak rotation ; but with a water cell 

 no motion was detectible. If the instrument be placed in a room at 

 15 Centigrade, in presence of a gas flame, there is rotation as usual ; 

 but if immersed in water at 45, the rotation is reversed. Lippmann 

 has given a very complete list of the theories which have been ad- 

 vanced to explain the motion of this instrument, the general conclu- 

 sion being that the energy effective is heat. 



Neeson has experimented at length on the so-called mechanical 



