228 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



acid dissolved in a little water is added, and the whole is 

 brought to boiling to favor the eolation of the iron. To the 

 cooled liquid, ammonia is added in quantity sufficient to ex- 

 actly neutralize the acids, and the precipitated hsematin al- 

 lowed to subside. This treatment is repeated so long as am- 

 monium sulphide discovers in the supernatant ammoniacal 

 liquid any trace of iron. The purified hsematin is finally dis- 

 solved in ether, the solution filtered, and the ethereal liquid 

 allowed to evaporate spontaneously. The pure coloring 

 matter is insoluble in water, slightly soluble in alcohol, but 

 readily so in ether, chloroform, carbon disulphide, and ben- 

 zene. It burns on platinum like a resinous substance, with- 

 out leaving any trace of ash. 6 J?, LXXIX., 918. 



FORMATION OF SULPHATES BY GAS FLAMES. 



A white incrustation is always formed after a short time 

 on the glass covers hung over gas flames. This incrustation 

 consists of small crystals of normal ammonium sulphate, with 

 a trace of soda and potash. The sulphur in the gas which is 

 burned to produce the sulphuric acid does not exist in the 

 condition of hydrogen sulphide, but in that of carbon disul- 

 phide. The ammonia is not a product of combustion, for if 

 a basin whose lower surface is moistened with hydrochloric 

 acid be held over a gas flame, there are no fumes visible, and 

 no ammonia is found even with the delicate reagent of Ness- 

 ler. But unburned gas contains a small quantity of ammo- 

 nia, enough to give a yellow color with the Nessler test. 

 Priwoznick has investigated this question, and supposes that 

 the ammonia comes from the nitrogen of the air, for Saussure 

 has shown that ammonia is formed when hydrogen is burned 

 in oxygen containing nitrogen. Schonbein proved the pres- 

 ence of ammonium nitrate in the products of combustion of 

 fat and of coal-gas. The carbon disulphide in the gas would 

 burn to carbonic and sulphurous dioxides. But sulphurous 

 oxide can not exist in presence of ammonium nitrite, but is 

 immediately oxidized to sulphuric acid and combines with 

 the ammonia. The glass cylinder of an argand lamp is also 

 often covered with a white incrustation. This consists main- 

 ly of potash, soda, lime, etc., from the ash of particles of 

 dust in the air. 14 (7, CCXIIL, 223. 



