270 



SCIENCE 



[X. S. Vol. XXXI. No. 790 



that is why when such oil film is completely 

 oxidized it ceases to accelerate corrosion. The 

 influence of various pigments when they form 

 parts of a linseed paint were discussed, and a 

 method for quantitatively measuring this influence 

 was described. It is believed that a development 

 of this method may show much concerning the 

 properties of ordinary protecting paint. 

 A Convenient Method of Refrigeration: J. O. 



Handy. 



Liquid air is most convenient for temperatures 

 below — 80° C. It costs $4 per liter and there 

 are losses and possible breakages of containers 

 which make its use in most cases expensive. 



Carbon dioxide is satisfactory down to — 78° C. 

 It is inefficient if used as a gas and not very sat- 

 isfactory when used as the solid CO, snow. 



The CO2 snow dissolves freely in acetone alcohol, 

 ether, gasoline and several other solvents of low 

 freezing point. These solutions absorb heat 

 rapidly from objects placed in them. They are 

 perfectly mobile and easily handled. 



Liquid carbon dioxide costs about 10 cents per 

 pound. Three and one third pounds of liquid 

 yield one pound of solid in two minutes if blown 

 from the original container through canvas bags. 



A mixture of 50 grams of CO2 snow and 150 

 grams of acetone had a temperature of — 63° C. 

 and caused one pound of mercury (freezing point 

 — 39° C.) to congeal in two and one half minutes. 



This method of refrigeration is useful for freez- 

 ing tests of oils, for condensation of volatile sub- 

 stances, for precipitation of substances like paraf- 

 fine from oil distillates and for general research 

 work. 



The Present Conditions of the Birch Oil Industry 

 in the United States : Edwaed Haet. 

 The industry is one of those classed by the cen- 

 sus takers as neighborhood industries and is car- 

 ried on for the most part in the Appalachian 

 plateau. The birch wood (Betiila lenta) is cut 

 into short pieces and distilled with water in primi- 

 tive stills. About 50,000 pounds are produced an- 

 nually. Oil of wintergreen (Gaultheria procum- 

 hens) is produced in the same way to the extent 

 of 5,000 pounds. Illustrations of the stills and 

 samples of the oil were shown. 



Variations in Car-painting Practise: Cael F. 



Woods. 



The four fundamental operations in car paint- 

 ing are filling the pores of the wood, smoothing 

 down the natural inequalities of the surface, 

 putting on the color in a smooth homogeneous 



film and finally covering the surface with a film 

 of varnish. The three methods are the " lead and 

 oil," the " surfacer " and the " color and varnish " 

 processes. The advantages and disadvantages of 

 the different methods are discussed. It is prob- 

 able that no one of the methods embody the maxi- 

 mum efficiency but it has been shown that a saving 

 of $20 to $30 can be made on the painting of 

 each car and an increase in life obtained of from 

 five to ten years by the adoption of scientific 

 methods of finishing. 



Some Variations in the Official Determination of 



Volatile Matter in Coal: A. C. Fieldee and J. 



D. Davis. 



Experimental data obtained in two different 

 laboratories bearing on the variations in the 

 volatile combustible matter, as determined in the 

 official method of the American Chemical Society, 

 are given in this paper, from which the following 

 conclusions are drawn: 



Laboratories using natural gas are apt to get 

 results on volatile combustible matter that are 

 considerably lower than those obtained in labora- 

 tories using coal gas unless the following pre- 

 cautions are observed: (1) Gas must be supplied 

 to the burner at a pressure of not less than ten 

 inches of water; (2) natural gas burners admit- 

 ting an ample supply of air should be used; (3) 

 air should be adjusted so that a flame mth a 

 short well-defined inner cone is produced; (4) the 

 crucibles should be supported on platinum tri- 

 angles and kept in a well-polished condition; (5) 

 semibituminous coals should be placed in an in- 

 clined position across the corner of the bottom of 

 the platinum crucible, to prevent the swelling up 

 of the coke in the early stages of the heat treat- 

 ment. 



Results by destructive distillation in a small 

 iron retort are practically the same as the official 

 volatile matter in the coal. 



Two laboratories may expect to vary as much as 

 2 per cent., both using the ofiicial method. 



The following papers are reported by title: 



Practical Corrosion Tests of Iron: W. D. Rioh- 

 aedson. 



Methods for Testing Commercial Anhydrous Liquid 

 Ammonia and Results: W. D. Richardson. 



The Temperature Reaction of Oil Mixtures loith 

 Sulphuric Acid: W. H. Botnton and H. C. 

 Sheeman. 



A Comparison of the Accuracy of Different Form- 

 ulcB for Calculating Fuel Values: H. C. Shee- 

 man and D. A. Baktlett. 



