194 



SCIENCE. 



[N. S. Vol. XXIV. No. 607. 



studied both from the strictly chemical 

 and from the industrial standpoints. Large 

 numbers of analyses of the wood of the 

 Norway pine and the Douglas fir as to the 

 amount of both the terpenes and colophon- 

 ium were made. The stumps and roots of 

 these species were likewise exhaustively 

 studied. A chemical examination of the 

 terpenes indicated that the common terpene 

 present differed from the pinene of the 

 southern pine, the boiling-point being 

 lower, the optical properties and the com- 

 pounds formed being different. A new 

 series of compounds, the chlor-hydroehlo- 

 rides, has been made both from the terpenes 

 above mentioned and from common pinene. 

 The colophonium from both the Norway 

 pine and the Douglas fir has been shown 

 to consist of two different acids. These 

 acids are being carefully studied. 

 JIarcourt and Esson's Method in Chemical 



Meclianics: W. Lash Miller. 



A§ the rate of a chemical change in a 

 homogeneous solution depends on the tem- 

 perature and on the concentrations of the 

 dissolved substances, measurements of the 

 rate are best made in solutions whose tem- 

 peratures are kept constant by means of a 

 thermostat and in which the concentrations 

 are kept constant by dissolving quantities 

 large in comparison with those generated 

 or destroyed during the reaction. In 1866 

 Hareourt and Esson measured rates of 

 change in solutions containing a large ex- 

 cess of each of the reagents but one. Al- 

 though they pointed out the advantages of 

 this method of working, their example was 

 not followed. Hood, in 1878, used in ex- 

 cess each but two of the reagents : van 't 

 Hoff ('Etudes,' 1884) used equivalent 

 quantities and compared the results of ex- 

 periments with different initial concentra- 

 tions; while from 1885 to 1895 it was the 

 custom to work with more or less equivalent 

 concentrations and to deduce the 'order' 



of the reaction from a series of analyses. 

 By this time the method of Hareourt and 

 Esson was forgotten. In 1895 A. A. Noyes 

 resuscitated van't Hoff's method; in 1901 

 Ostwald proposed a method which some- 

 what resembles Hareourt 's ; and in the same 

 year Hareourt and Esson's way of work- 

 ing was revived in the laboratory of the 

 speaker, where the principles of the method 

 have been extended (method of constant 

 rates) and applied to the study of chemical 

 equilibrium (arsenic and iodine). The 

 power of Hareourt and Esson's method as 

 a tool of research was illustrated by a num- 

 ber of examples. 



Some Problems for Agricultural Chemists: 



E. B. VOORHEES. 



This paper is historical and suggestive, 

 rather than containing the results of 

 definite experiments. It points out the 

 conditions heretofore existing in this coun- 

 try, which have encouraged agricultural 

 chemists to demonstrate the principles al- 

 ready understood, rather than to investi- 

 gate. Notwithstanding the larger use of 

 commercial fertilizers in the east, and better 

 farming methods in the west, there is an 

 apparent exhaustion of soils, which calls 

 for scientific investigation of those prob- 

 lems connected with the soil and its fer- 

 tility. 



The nitrogen question is supreme, not- 

 withstanding the discoveries that have re- 

 cently been made, in reference to both the 

 symbiotic appropriation of nitrogen, and 

 its abstraction from the air by electric 

 means. 



The Occurrence of Boracic Acid in Death 

 Valley, California, and in Tuscany: Ed- 

 ward Hart. 



This was a description of two trips, one 

 to Death Valley in 1902-3 and one to the 

 soffoni of Tuscany in May, 1906. The 

 boric acid occurs near Daggett, California, 

 as eolemanite, CagBeOn, and as calcium 



