October 9, 1896.] 



SCIENCE. 



539 



whereas in the 16th fractionation the 



temperature range (AO gives, as a rule, a 

 measure of the purity of the liquid, though iu 

 the early fractionations of a complex mixture 

 this cannot always be relied on. Thus, in the 

 4th fractionation, the fraction coming over 

 between 65° and 66° had the highest value of 



A< 



corresponding fraction (65° to 66.85°) had the 

 lowest value. In th6 first case a mixture of nor- 

 mal and iso-hexane was separating rapidly from 

 the pentanes and heptanes in the petroleum 

 «ther ; in the second considerable progress had 

 been made in the separation of normal from iso 

 hexane (B. P" 69°0 and about 61° respectively). 



After the 16th fractionation it was decided to 

 proceed at first with the separation of normal 

 hexane only, and after the 31st preliminary 

 fractionation it was considered that the separa- 

 tion had proceeded far enovigh for the final 

 series of fractionations to be undertaken {loc. 

 cit.). 



The normal hexane obtained by the final 

 fractionation of the fractions boiling at and 

 a,bove 69.1°, when distilled from phosphorus 

 pentoxide, boiled at 69.1° or 0.1° higher than 

 the hexane from propyliodide; its specific 

 gravity at 0° was 0.68478 or 1.15 per cent, 

 higher. 



The hexane was, therefore, shaken repeatedly 

 with a mixture of concentrated nitric and sul- 

 phuric acid, when considerable heat was 

 ■evolved and some ni-dinitrobenzene was 

 formed. The impurity, which could not be 

 separated by fractional distillation, was, there- 

 fore, benzene with, possibly, some hexanaph- 

 thene. 



The other fractions were separately treated 

 with the mixed acids and after further fraction- 

 ation a product was obtained boiling at 69.05° 

 and with the specific gravity 0.67813 at 0° or 

 only 0.17 per cent, higher than that of pure 

 hexane. 



The boiling points, specific gravities and 

 critical constants of the two specimens of nor- 

 mal hexane are given below: 



Normal Hexane Normal Hexane 



from from 



Propyl Iodide. Petroleum Ether. 



Boiling point 69.0° 69.05° 



Specific gravity at 0° 0.67696 0.67813 



Critical temperature 234.8° 235.15° 



Critical pressure..... 22510 mm. 22560 mm. 



Critical volume of a gram. ..4. 268 cb. cms. 



SOME EECENT MEXICAN PUBLICATIONS. 



Mexican men of science are doing much ac- 

 tive scientific work, as is shown by the extent 

 and value of the following publications : 



1. Biblioteca Botdnieo-Mexicana. Catalogo Bib- 

 liografico, Biografico y Critico de Autores y 

 Escritos Beferentes a Vegetales de Mexico y sus 

 Aplicaciones, desde la Conquesta Hasta el Pre- 

 sente. Escrito por el Dr. Nicolas Leon, 

 Mexico, 1895. 



This work of 375 pages is comparable to 

 Sereno Watson's Bibliography of American 

 Botany, issued a number of years since. The 

 number of separate entries in the main alpha- 

 betically arranged list is 805, making, with those 

 of the appendix (82), a total number of titles 

 quoted of 887. The work aims at being a com- 

 plete list of the floras and books, as well as 

 papers and sepai-ates, dealing with the plants of 

 Mexico published since the Conquest. A fair 

 number of American authors are cited, and 

 their botanical work reviewed briefly or at 

 some length ; among such may be mentioned 

 Audubon, Bailey, Chapman, Eaton, Eggers, 

 Engelmann, Gray, Parry, Pursh, Riley, Rose, 

 Rotlrrock, Torrey and Trelease. Short bio- 

 graphical sketches of the botanists who ex- 

 plored Mexico, as far as known, are added, as 

 also an account of their work while in the field 

 and the extent and importance of their collec- 

 tions. Botanists of the United States, Canada 

 and Europe not familiar with this comprehen- 

 sive work would do well to procure a copy from 

 the author or from the printer in the city of 

 Mexico; Oficina Tip. de la Secretaria de Fo- 

 mento. 



2. Informe que rinde d la Secretaria de Fomento. 

 El Director del Instituto Medico Nacional Dr. 

 Fernando Altamirano. Sohre algunas ex- 

 cursiones d las Montanas del Ajusco y Serrania 

 de las Cruces. Mexico, 1895. 



This pamphlet of some 64 pages gives an ac- 

 count of a new amphibian Amblystoma Altami- 

 rani, A.Duges, with a colored lithographic 

 plate of the same, as well as an account of an 



