ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 825 



sion will retain its efficiency for the purpose of these tests for a period 

 of from four to eight weeks. When shaken up, the suspension should 

 be homogeneous and of a greyish-white colour. It should not agglutinate 

 in the presence of a normal serum in a dilution of 1 in 50. Spontaneous 

 agglutination may take place if the washing process is too thorough. 



The test is carried out in a similar manner to that used with bacterial 

 emulsions. The serum under observation, in suitable dilutions, is put 

 in tubes with equal quantities of the suspension. Controls are also put 

 up. The tubes are incubated for (5 to 12 hours, and, if necessary, allowed 

 to stand at room temperature for 20 hours after incubation. When 

 examining the tubes, it is necessary to shake them up and examine the 

 floating particles. It is not easy to distinguish degrees of agglutination. 



SojniERPELDT, E. — Ueber die Fortschritte der mikroskopischen untersuchungs- 

 methoden fur mineralogie und analytische chemie wahrend der letzten Jahre. 



Zeitschr. wiss. Mikroskr. xxviii. (1911) pp. 183-206 (2 figs.). 



Metallography, etc. 



Aluminium-magnesium Alloys.*— W. Broniewski has made deter- 

 minations of the various electrical properties of alloys of aluminium 

 and magnesium ; the results indicate the existence of two compounds, 

 AlMg and Al 2 Mg 3 . Alloys corresponding to the formula? Al 4 Mg and 

 AlMg 2 were found to be heterogeneous in microstructure. 



Bismuthides.f — A. G. Vournasos has prepared sodium bismuthide 

 Na 3 Bi, the existence of which is indicated by thermal analysis of the 

 system, by adding bismuth to sodium melted under paraffin. Potassium 

 bismuthide K 3 Bi is obtained in a similar manner. 



Arsenides of Tin.:}: — P. Jolibois and E. L. Dupuy have prepared 

 alloys by heating known weights of arsenic and tin together in sealed 

 tubes, at 650° C. Sections for microscopical examination were etched 

 with ferric chloride solution. The presence of the compounds Sn 4 As 3 

 and SnAs was indicated. 



A thermal investigation of the arsenic-tin system by N. Parravano 

 and P. de Cesaris § indicates the existence of the compounds Sn 3 As 2 and 

 SnAs. 



Alloys of Silver with Cadmium. || — G. J. Petrenko and A. S. 

 Fedorow have made a thermal and microscopical investigation of the 

 silver-cadmium system. Six series of solid solutions, with intervening 

 gaps, are formed. The compound AgCd results from a reaction oc- 

 curring in the solid state. The compounds AgCd 3 and Ag 2 Cd 3 are 

 probable. The existence of AgCd 4 was disproved by quenching experi- 

 ments. 



* Comptes Rendus, clii. (1911) pp. 85-7 (6 figs.). 

 t Comptes Rendus, clii. (1911) pp. 714-15. 

 $ Comptes Rendus, clii. (1911) pp. 1312-14. 



§ Atti R. Accad. Lincei, xx. (1911) 1, pp. 593-G, through Journ. Chem. Soc, c. 

 (1911) p. 613. 



|| Zeitschr. Anorg.Chem.,lxx.(1911) pp. 157-69; lxxi. (1911) pp. 215-18 (15 figs.). 



