71 Scientific Intelligence. 



trated sulphuric acid, or by the action of concentrated sulphuric 

 acid on hydrogen peroxide. These chemists were unable to 

 obtain the acid in a pure state or to prepare any salts of it, but 

 by'studying the behavior of hydrogen peroxide, Caro's acid, and 

 persulphuric acid they found that the first substance could be 

 determined and destroyed in the presence of the others by means 

 of potassium permanganate, and that Caro's acid liberates iodine 

 immediately from acidified potassium iodide solution, while with 

 persulphuric acid this liberation is very slow. By applying these 

 facts they were able to determine the ratio of the oxygen to the 

 sulphuric acid liberated by the acid under investigation, and the 

 conclusion was reached that it has the composition represented 

 by the formula H 2 S0 5 . The probable structure of the acid is 



rr r\ 



tt/~v_o^S0 2 . The change from persulphuric acid to Caro's acid, 



which takes place gradually in solution, is as follows : 

 HAO B +H 2 = H 8 S0 5 +H,SO, 



Caro's acid is then gradually changed in solution to sulphuric 

 acid and hydrogen peroxide according to the equation, 



In the presence of strong sulphuric acid the last equation is 

 reversed to a certain extent, but the product still contains much 

 unchanged hydrogen peroxide. — Berichte, xxxiv, 853. h. l. w. 



3. Vitrified Quartz. — In a recent discourse delivered before the 

 members of the Royal Institution in London, W. A. Shenstone 

 exhibited the production of tubes and bulbs of fused silica. The 

 first stage of the process consists in getting quartz into a condi- 

 tion in which it will not fly to pieces when heated. This is done 

 by heating it in small fragments to about 1000° and throwing it 

 quickly into cold water. It then becomes white and enamel-like, 

 and after the treatment has been repeated it may be thrust sud- 

 denly into the hottest part of an oxyhydrogen flame without 

 splintering to the slightest extent. Silica becomes hot enough to 

 be worked only above the melting-point of platinum, and it is 

 only the hottest part of the oxyhydrogen flame, just beyond the 

 inner blue cone, where the temperature is sufficient for the pur- 

 pose. To produce tubes and other vessels from the enamel-like 

 silica, two fragments of it held in platinum forceps are heated 

 and pressed together until they adhere, then other lumps are 

 added, one at a time, until a rough rod is produced. This rod is 

 afterwards reheated and drawn out into a finer rod about l mm in 

 diameter. Some of these fine rods are then bound round a stout 

 platinum wire, while soft, and heated until their sides adhere. 

 The rough tube thus made is reheated, drawn out and, after being 

 closed at one end, a bulb is blown in it. By applying thin rings 

 of silica to the small bulb, heating until the silica begins to spread 

 and blowing out, it is increased in size, and by drawing out such 

 bulbs long tubes may be prepared. When a silica tube has been 

 produced it may be worked in the flame as easily, though not as 



