. Rapport sur l'enquête forestière du Ministère de l'agriculture. 1877-1898. Les forêts et la foresterie. Les enquêtes sur les résines. 337 c soustraite de celle de b d'obtenir l'humidité JZ. L'échantillon de bois de chauffage est alors épuisé par l'éther, ce dernier s'est évaporé, et le résidu est chauffé à environ 140° à 150° jusqu'à poids constant ; cela donne à l'rosin B. Si l'être la perte totale par extraction à l'éther, nous avons mais il a rapidement été trouvés par des expériences sur l'huile de térébenthine pure que les deux tubes de CaCl3 n'a pas retenu une quantité égale d'huile volatile. La quantité retenue dépend

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. Report upon the forestry investigations of the U. S. Department of agriculture. 1877-1898. Forests and forestry. INVESTIGATIONS INTO RESINS. 337 c subtracted from that of b would then give the moisture JZ. The sample of wood shavings is then exhausted with ether, the latter evaporated, and the residue heated at about 140° to 150° to constant weight; this gives the rosin B. If L be the total loss by extraction with ether, we have But it was soon found by experiments upon pure turpentine oil that the two CaCl3 tubes did not retain an equal amount of volatile oil. The quantity retained depended upon many circum- stances, the chief one being the amount of moisture already present in the CaCl2 tubes. Even had the tubes retained quantities of turpentine oil, this method would still have the objection that one of the constituents was to be determined by difference—an objection especially serious when the ingredient to be so determined is small in comparison with the materials to be weighed. The writer has therefore attempted to make use of a somewhat different principle. A few trials were sufficient to show that the method promised to give satisfactory results. The basis of the method is the same which served for the production of Eussian turpentine oil on a large scale, namely, the distillation of the volatile products from the wood itself, without previously obtaining the turpentine. But instead of condensing the volatile products, their vapors are passed over heated copper oxide, whereby they are burned to water and carbon dioxide. Many trials were made with this method upon pure materials and on samples of resinous wood. As the results were found to be entirely concordant and satisfactory, the method was adopted, and by it were obtained the results presented in this report. DESCRIPTION OF THE METHOD EMPLOYED. A weighed amount of wood shavings is placed in a straight CaCl2 tube a. The tube is con- nected on one side by means of a capillary tube with a drier A, whi

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