218 SUMMARY OF CURRENT RESEARCHES RELATING TO 



foregoing precedure. Stain with the aid of heat by means of the petrol- 

 ether-carbol-fuchsin solution. Then treat for 5 minutes with iodo- 

 potassic iodide solution. Decolorize for 10 seconds in 3 p.c. hydro- 

 chloric acid, wash in aceton-alcohol (equal parts) until no more colour 

 comes away. Contrast stain with 2 p.c. safranin solution. 



(6) Miscellaneous. 



Biochromo-reaction for Diagnosis of Typhoid Bacilli.*— In order to 

 facilitate the recognition of typhoid bacilli in faeces, water, etc., Botelho 

 has devised an application of the principles of vital staining and agglutin- 

 ation. A dilution of the material to be examined is treated with a blue 

 stain ; a suspension of known typhoid bacilli is treated with a red stain. 

 Serial dilutions of a standard typhoid agglutinating serum in a gum 

 solution are prepared. By means of a platinum needle portions of the 

 known and the unknown suspensions are added to drops of the dilutions 

 of the agglutinating serum, the blue and the red baciUi are side by 

 side in this fluid. If agglutination of red and blue bacilli together be 

 observed, the reaction is said to be positive. Separate agglutinations of 

 the known typhoid and of the unknown organisms is interpreted as 

 negative, the blue agglutination being regarded as non-specific clumping. 

 Only when organisms from the two sources, distinguished by their 

 staining, appear together in a clump, may the presence of typhoid 

 bacilli in the material under investigation be inferred. 



Metallography, etc. 



Iron-carbon Alloys. f — Wittorf's investigations upon the iron- 

 carbon equilibrium in the hypereutectic region are summarized by 

 Belaiew. By observations of the phenomena occurring when iron is 

 heated with excess of carbon at temperatures up to 2600° C, and by 

 microscopic examination of melts quenched from different temperatures, 

 the existence of three phases which are probably compounds having the 

 formulse FeC2, FeO, re4C, has been established. Fe02 in the form of 

 primary crystals is silvery grey in colour, is attacked sloAvly by 20 p.c. 

 nitric acid in water, and deposits copper from a dilute solution of copper 

 sulphate. 



System Iron-iron sulphide.J — R. Loebe and E. Becker have in- 

 vestigated the Fe-FeS system thermally, and describe the structure of 

 numerous alloys prepared. Alloys containing 64 and 74 p.c. FeS, after 



* C.R. Soc. Biol. Paris, Ixxiii. (1912) pp. 692-4. 



t Rev. M6tallurgie, ix. (1912) pp. 600-17 (26 figs.) See also Vorlaufige Ver- 

 suche iiber primare Kristallisation und nachfolgende physikalisch-cheniische Um- 

 wandlungen im Systeme : Eisen-Kohlenstoff mit iiber 4% Kohlenstoff, N. M. 

 Wittorf, Zeibschr. Auorg. Chem., Ixxix. (1912) pp. 1-70 (42 figs.). 



X Zeitschr. Anorg. Chem., Ixxvii. (1912) pp. 301-19 (24 figs.). 



