402 KECORD OF SCIENCE FOR 1886. 



sure success. The use of a shallow vessel to allow a large contact surface 

 with the freezing mixture; the Ba02 must be added very slowly to pre- 

 vent too great a rise in temperature, and stirred constantly. The Ba02 

 should be added until the mixture shows a slight alkaline reaction to 

 insure the complete precipitation of BaHP04, asthis compound is solu- 

 ble in acids. The solution is freed from dissolved barium by addition 

 of diluted sulphuric acid, and the insoluble precipitate removed by fil- 

 tration. 



In order to prevent the decomposition of the H2O2, the temperature 

 should not be allowed to rise above 40° or 45° F. The reaction in this 

 process is explained in the following equation: Ba02-|-H3P04=BaHP04 

 + H2O2. 



The solution obtained is sufficiently concentrated for most purposes to 

 which it is applied, and is much stronger than much of that found in 

 commerce. (Pharm. News, vi, 148.) 



Hydrogen Peroxide and its Estimation, by Maurice de Thierry.— Since 

 its discovery by Th6nard in 1818, hydrogen peroxide has remained a 

 mere chemical curiosity, but it has recently acquired industrial impor- 

 tance. It is now used not only for restoring blackened oil paintings, but 

 a large quantity is consumed in bleaching ostrich feathers, silk, and hair. 

 When pure, peroxide of hydrogen has a density of 1.454, but the com- 

 mercial product is much weaker ; its activity being dependent on its con- 

 centration the author has devised a method for determining the value 

 of samples. The method is based on the decomposition by manganese 

 dioxide and is conveniently carried out by means of the simple appara- 

 tus figured in the original memoir. (Comptes Eendus, cii, 611.) 



Hydrates of Sulphuric zicid. — At the January meeting of the Russian 

 Chemical Society Professor MendelejeflF communicated some results of 

 his investigations into the thermic effects of dilution of sulphuric acid 

 with water. The maximum evolution of heat, and the maximum contrac- 

 tion of 100 parts of the solution both correspond to the solution contain- 

 ing from 65 to 75 per cent, of H2SO4, which is very near the hydrate 

 H6S06=S(OHj6. Together with some other observations this leads the 

 author to the conclusion that there exist at least five more or less con- 

 stant hydrates of sulphuric acid, viz, H2SO4, H4SO5, HgSOe, and two 

 more containing a large amount of water, as H2SO4-i-100 H2O. (Nature, 

 XXXIII, 591.) 



Decomposition of Ammonia by Electrolysis, by the Rev. A. Irving. — 

 The author electrolyzes a concentrated solution of sodium chloride, 

 with which is mixed about one-tenth its volume of the strongest solu- 

 tion of ammonia. The solution is placed in an ordinary three-tubed 

 voltameter of Hofmann's form, into which carbon pencils are introduced 

 (with the aid of corks), to obviate the action of nascent chlorine on plati- 

 num were this metal used for the electrodes, With four to six Buusen 



