170 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



I. The Determination of Nitrous and Nitric Acids. — Weisen- 

 heimer and Heim describe a convenient method for the gaso- 

 metric determination of either or both of these acids. The 

 operation is carried out with a flask of 50 cc capacity, in which the 

 slightly alkaline solution of the substance (containing -1 to "2 g. of 

 nitrite) is placed. Carbon dioxide is led in from a Kipp's gener- 

 ator through a tube reaching below the liquid in the flask, and a 

 delivery tube is attached which ends in a turned-up point in a 

 trough containing 12 per cent sodium hydroxide, in such a man- 

 ner that an eudiometer filled with the sodium hydroxide solution 

 may be placed over the outlet. A funnel tube provided with a 

 pinch-cock is placed in the third hole of the rubber stopper of the 

 flask. The stem of this funnel tube is narrowed at the end and 

 it is filled with water up to the funnel at the beginning of the 

 operation. The apparatus is first freed from air by passing car- 

 bon dioxide through it, then 10 or 15 cc of a five per cent solution 

 of potassium iodide are introduced, and then, slowly, the same 

 amount of dilute hydrochloric acid. All the nitrous acid is thus 

 converted into nitric oxide according to the equation 



HN0 2 + HI = NO + 1 + H 2 0. 



The liquid is slowly raised to the boiling-point and the gas is 

 swept over into the eudiometer by the stream of carbon dioxide, 

 and is measured. When nitric acid is to be determined, a newly 

 filled eudiometer is placed over the delivery tube, 10 or 20 cc of a 

 concentrated solution of ferrous chloride in strong hydrochloric 

 acid are introduced, and the gas formed according to the equation 



HN0 3 + 3FeCl 2 + 3HC1 = NO + 3FeCl 3 + 2H 2 



is collected and measured as before. Test analyses with nitrites 

 and nitrates alone, and with mixtures of both, gave very satisfac- 

 tory results. The method has the advantages of being rapid and 

 in furnishing direct determinations of both acids in a single sam- 

 ple of substance. — Berichte, xxxviii, 3834. h. l. w. 



2. The Modifications of Antimony — Stock and Siebert have 

 found that, like arsenic, antimony exists in a yellow, a black, and 

 a metallic gray modification. The last is the most stable form, 

 and the only one heretofore mentioned in chemical literature. 

 The black modification may be obtained by heating the yellow 

 form to temperatures above —90°, by the action of oxygen upon 

 liquid antimony hydride above —90°, and also by the sudden 

 cooling of the vapor of ordinary antimony. Its specific gravity 

 is 5 - 3, while that of the ordinary metal is 6 "7. It is chemically 

 active, often igniting when exposed to the air. It is changed 

 into metallic antimony by heating, the change being instanta- 

 neous at 400°. The authors consider the black precipitates pro- 



