Mabch 18, 1904.] 



SCIENCE. 



445 



a class of compounds is obtained of the 

 general type 



wliere x is any halogen. These compounds 

 he designated as the acetines of lead. 



It is well known that lead sulphate is 

 soluble in alkaline acetates, tartrates, etc., 

 and experiment shows that the halogen 

 salts of lead are also soluble under like 

 conditions. It seems probable that these 

 in passing into solution may form com- 

 pounds of similar character to those men- 

 tioned above. 



To test this, experiments were planned, 

 whereby the products of the reaction might 

 be collected and examined. Lead iodide 

 was chosen for the preliminary experi- 

 ments, because it was found that the prod- 

 ucts resulting from its solution in acetates 

 and tartrates is white, hence the reaction 

 could be followed by observing the change 

 of color. 



The following method of preparation of 

 the salts was adopted : A very concentrated 

 solution of the acetate to be used was first 

 made in alcohol, the strength of which was 

 adjusted for each case, varying from 50 

 to 95 per cent. To this a few drops of 

 glacial acetic acid were added — otherwise 

 the lead iodide is transformed almost en- 

 tirely into the basic iodide — and then 

 freshly precipitated lead iodide was 

 brought into the hot solution until it was 

 nearly saturated, the solution filtered and 

 allowed to cool in a vacuum over sulphuric 

 acid. 



In each case, upon cooling, well-defined 

 colorless crystals were obtained, which, 

 after draining off and washing with a mix- 

 ture of strong alcohol and ethyl acetate, 

 were subjected to analysis. In no case, 

 however, was the simple compound 



1 C2H3O2 



corresponding to Carius's salt obtained; 

 instead, the analyses showed that com- 

 pounds were formed, which may be inter- 

 preted as a combination of this with the 

 metallic acetate used. The following salts 

 have so far been isolated and analyzed : 



■"■■ ^^ 1 CjHsOj+NaC^HaOj • ^QH^O^, 



melting point (uncorr. ) 124-125° C. 



^'"' ^^ I CjHA + SNaCjHsOj ■ iC^HjOj, 



melting point undetermined. 



III. Pb I Q^gf^Q^ _|_ Kc^HjO,, 



melting point 208-208.5° C. 



IV Pb I 



• ''"IC2H3O2-I-NH1C2H3O2, 



melting point 166-167° C. 



V Pb i 



"^ ■ ""^ 1 C2H3O2 + PblC^HjOj), ■ JC^HA, 



melting point 202-205° C. 



They all (with the exception of II.) pos- 

 sess a characteristic crystal form and give 

 fairly sharp melting points. It will be- 

 observed that some of them contain acetic- 

 acid of crystallization, while others do not,, 

 although they were all prepared in a sim- 

 ilar manner. When dry they are quite 

 stable, but are decomposed by water or 

 moist air, forming first lead iodide, then 

 the basic iodide. Organic solvents are 

 without action. On account of the insolu- 

 bility and general inactivity of these sub- 

 stances, it has not yet been possible to 

 determine with positiveness their molecular 

 structure. It is hoped that fiirther investi- 

 gation may throw additional light upon this 

 point. 



The Theory of Valence: G. B. Frank- 

 FOETER, University of Minnesota, Min- 

 neapolis, Minn. 



Valence followed, as a natural conse- 

 quence, Dalton's atomic theory and the 

 laws of definite and multiple proportion. 

 The first real expression of the present 

 valency theory was made by Frankland, 

 followed by Kolbe and others, who showed 



