936
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
The conclusion from these curves is that by drying a t 105" for one hour in an atmosphere of air, the loss whatever it is, has reached a constant quantity. //
1 1 I P J;p / o,/ y h l l ! l I
platinum lined and under adiabatic control by having accessible both hot and cold water for modifying the temperature of the jacketing water to conform to the inner system containing the combustion bomb. The circulation of the jacketing water is secured through the cover as well as on all sides and bottom of the inner receptacle. The results are given in Table I. Corrections were made for the nitric acid formed in the combustion, the fuse wire, etc., as prescribed by the standard method adopted by the AMERICANCHEMICAL SOCIETY.' TABLE I Per cent Hz0 B. t. u. (as WOOD a t 105O C. 1 hr. Recd.) Pine 8.88 8040.0 8055.5 8054.0 AVERAGE.. .8049.8 Oak 8.35 7829.0 7855.5 7840.0 AVERAGE.. .7841.6 Hickory 10.30 7594 2 7561.0 7578.8 AVSRAGE.. 7578.0 Cherry 8.85 7852.0 7867.7 7860.0 AVERAGE.. 7859.9 Birch 10.18 7607.2 7593.0 7692.2 AVERAGE.. 7597.4 Poplar 10.69 7709.8 7725.2 7712.5 AVERAGE., 7716.1
Hours o f H e o f / h g of /37' C /n CO,
FIG.
2
One other set of curves is worth noting. In Fig. 2 the temperature used was 137" and the atmosphere was carbon dioxide in order to eliminate possible oxidation from the presence of free oxygen. Here the values are stabilized a t the end of the first hour, but they are in most cases a trifle higher, usually about 0.2 to 0 . 3 per cent, though in the case of birch and hickory the difference is not appreciable. The conclusion from a comparison of these two charts suggests the probability of a slight loss of volatile constituents other than water at the higher temperature. This was verified by repeating the drying on a few samples, using the higher temperature with an atmosphere of air and collecting and weighing the water discharged. The apparatus used is shown in outline in Fig. 3. It is a slight modification of the apparatus described by Prof. John Whites6 The drying chamber is maintained at 135" to 140°,it being surrounded by xylene vapor, The loss in weight is consistent with the loss as shown in Fig. 2. The weight of water absorbed is uniformly less than the total decrease in weight, verifying the point already noted that some volatile constituents of the wood other than water are discharged at 136" to 140". This material is so small a t this temperature, averaging about 0 . 3 per cent, that it is considered negligible at a drying temperature of 105". It is, at any rate, of the same order of difference between water and volatile constituents as the material commonly recognized as being discharged from coal under the same conditions of drying. I n determining the calorific values, the same samples were employed with the moisture content taken as &own after one-hour's drying as in Fig. 1, the heat values being calculated to the dry basis. The instrument used was of the Mahler type, e
J . Frank. Inst., 173 (1913), 201.
VoI. 14, No. 10
B. t. u. (Dry Basis)
...........
8836.2
...........
8555.7
..........
8448.1
..........
8623.0
..........
8458.4
..........
8639.6
A comparison with the values as given by Gottlieb for corresponding varieties of wood, so far as they were represented in our samples, will be of interest as follows: T A B L11-B. ~ WOOD Oak Pine Birch
GOTTLIEB
8316 9153 8586
T. U. VALUES PARRAND DAVIDSON
8555.7 8836.0 8468.4
DIFFERENCE
4-239.7 -317.0 -127.6
An inspection of the table shows that the Gottlieb results have a variation from our own of A3 per cent. Considering the fact that woods, even of the same varieties, grown in different countries indicate no greater divergence, it is fair to conclude that the values obtained by Gottlieb should be accepted as reasonably accurate. It must be concluded, however, that considering the care and type of instrument employed in this work, the values as given in Table I fairly represent the correct heat values for the several samples worked on and may be taken as representative values for American woods. 7
"Report on Sampling and Analysis of Coal," THISJOURNAL, 6 (1918).
517.
New Standard Sample of Bureau of Standards A new standard sample of tin-base bearing metal No. 54 is now being issued with a provisional certificate. This sample has the approximate composition: Tin 88 per cent, antimony 7 per cent, and copper 4 per cent. In addition it contains small amounts of lead, iron, bismuth, and arsenic. The price of this sample is $2.00 per 140 g., prepaid orparcel post C. 0. D. Benzoic acid No. 48a and benzoic acid No. 39a have been discontinued. Benzoic acid No. 39b replaces both of these and is issued for use both in acidimetric and calorimetric work. The price of this sample is $2.00 per 30 g.
