238 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1 . The Manufacture of Sulphuric Acid by the Contact Process. 

 — In an address before the German Chemical Society Knietsch 

 has given an interesting account of the development of a method 

 for the manufacture of sulphuric acid which is evidently destined 

 to revolutionize this great industry, in supplanting the use of the 

 old lead-chamber method. Since 1831, when Phillips in England 

 discovered the fact that sulphur dioxide and oxygen can be made 

 to combine in contact with finely-divided platinum, many efforts 

 have been made to apply this and . other catalytic agents to the 

 practical manufacture of sulphuric acid, but until within a few 

 years the problem has remained unsolved. The success of the 

 process at the " Badische Anilin- und Soda-Fabrik " has been due 

 to a long series- of carefully conducted experiments. A serious 

 obstacle encountered was the difficulty of properly purifying 

 the gases from the pyrites-furnaces so that they would not 

 quickly destroy the activity of the platinum, which is used in 

 the form of platinized asbestos. Traces of arsenic were found 

 to be one of the chief causes of this trouble, and by proper cool- 

 ing and washing, and by actually filtering the gases it was finally 

 possible to remove all solid particles, so that the platinum 

 remained effective for an unlimited time. It was found that a 

 temperature of about 450° C. is most favorable for the reaction, 

 hence instead of heating the platinized asbestos, as was formerly 

 thought necessary, it has been found desirable to cool it after the 

 process has been started. The fact that the mass action of an 

 excess of one of the reacting gases has an important influence 

 upon the completeness of the reaction was discovered ; hence the 

 reaction is practically complete with the gases from pyrites 

 burners containing about three times the necessary oxygen. The 

 process is particularly adapted to the manufacture of fuming sul- 

 phuric acid and the anhydride, but there can be little doubt that 

 it will be the method of the future for the production of the 

 ordinary acid. The statement is made that the production of 

 sulphuric anhydride by this process at the " Badische " works 

 amounted to 116,000 tons in the year 1900. The address as pub- 

 lished gives many valuable data in respect to the physical 

 properties of all strengths of sulphuric acid, including the melt- 

 ing-point 5 specific-gravity, specific heat, heat of solution, electri- 

 cal resistance, action on iron, boiling-point, vapor-pressure, vis- 

 cosity, and capillary action. — JBerichte, xxxiv, 4069. h. l. w. 



2. Metallic Carbides. — Motssan has recently published a 

 review of the present knowledge of this subject, to which he has 

 been the most prominent contributor. The following carbides 

 are not decomposed by water : Fe 3 C, Cr 3 C 2 , Cr 4 C 3 , Mo 2 C, WC, 

 W 2 C, VC, ZrC, and TiC. The iron carbide, Fe 3 C, exists in 



