CHEMISTRY. 189 



ultimately black. To avoid the reduction of the carl)on, the heat 

 should be moderated in the latter part of the operation, and the 

 whole slowly cooled. Left in the air to oxidize, and then ex- 

 hausted with water, about one-tenth of the mass is found to be 

 oxalate of soda. In the same way oxalate of potassa may be 

 obtained from an amalgam containing 2 per cent, of potassium. 



CHEMICAL CALCULUS. 



Sir Benj. C. Brodie, Professor of Chemistry in the IJniversit}'' of 

 Oxford, in a lecture " On the Mode of Representation atForded by 

 Chemical Calculus as contrasted with the Atomic Theory," assumes 

 as his unit that portion of j^onderable matter which at the melting- 

 point of ice, and at a pressure of 760 millimetres of mercury, oc- 

 cupies a space of 1,000 cubic centimetres. To denote units of 

 chemical substances, he uses Greek letters as symbols, and in such 

 a manner as to indicate that nitrogen, phosphorus, chlorine, bro- 

 mine, iodine, and several other so-called elementary substances, 

 are compounds containing hydrogen, in combination with luiknown 

 elements. It is claimed that this system shows there are three, 

 and perhaps four, fundamentally distinct classes of elemental 

 bodies. The first may be represented by hydrogen and mercur}^ ; 

 the second by oxygen and sulphur; the third by nitrogen and 

 chlorine. The only novelty in this classification is the grouping 

 together of elements of widely differing '* atomicity." What ad- 

 vantages may be gained by assuming that substances not yet de- 

 composed are compounds, and using symbols of volumetric units 

 as a more mathemetical form of expression, the author has not yet 

 satisfactorily shown. 



CHEinCAL NATURE OF CAST IRON. 



A "Report on the Chemical Nature of Cast Iron," by Dr. A. 

 Matthiessen, read before the British Association in 1868, was im- 

 portant, inasmuch as it stated that although he and Dr. Prug had 

 made seventy experiments in the production of pure metallic iron 

 from its various compounds, they had not succeeded in obtaining 

 any iron perfectly free from sulphur. He hoped, however, by 

 continuing his researches, to obtain a perfectly pure sample of 

 metallic iron. 



In the course of the discussion which followed, Mr. Sutton sug- 

 gested that probably the presence of sulphur in iron was only 

 another instance of the persistence of that element in the atmos- 

 phere, as shown by the experiments of Mr. W. F. Barrett, who 

 first devised the method of detecting the presence of sulphur upon 

 the surfaces of bodies exposed to the air, by projecting upon them 

 a flame of liydrogen, a magnificent blue flame resulting there- 

 from. 



ky^ 



