INDUSTRIAL AND ENGINEERING CHEMISTRY
30
The toxicity of zinc meta-arsenite has been studied in the case of Fornes annosus, and it was thought desirable to extend these tests to the other fungi which were available, Some of these had not been used for experimental work for several months and it was found that the pure cultures of Lentinus lepideus, Lenzites sepiaria, and Polyphorus pilotae were dead. The others were in good condition, however, and were used in the toxicity tests, the details of which are given in Table 111. The cultures were made with zinc meta-arsenite in powder form dispersed through the gel, as any attempt to precipitate the preservative in situ would probably result in the presence of a small quantity of free arsenious oxide in the culture. This method is unfair to the preservative as uniform dispersion of the particles of powder is very difficult to attain. The gel is, of course, non-toxic between the particles. Wood treated with zinc and copper arsenites shows, after seasoning, a very effective distribution of preservative. Microtome sections of yellow pine containing copper arsenite were stained with dilute potassium ferrocyanide and examined at 1500 diameters magnification. Untreated zones showed no color with the reagent while those parts containing copper were colored pink to mahogany. Photomicrographs showed heavy deposits of preservative in the medullary rays and resin ducts where fungous attack was most severe and lighter uniform deposits in the cells and cell walls. Microscopic studies on wood treated with zinc meta-arsenite indicate a distribution similar to that observed in the case of copper arsenite. We have found no stain which colors the crystals so effectively as ferrocyanide on copper. While the distribution of preservative in the gel is by no means comparable with that actually attained in wood, the tests may be of value if the shortcomings of the method are borne in mind. Table I11 shows the effect of powdered zinc meta-arsenite on the various fungi. A (-) indicates no culture of the fungus a t the given concentration of preservative. If there could be obtained a distribution of preservative in nutrient gel equal to that in wood treated under commercial conditions, it is believed that all the fungi listed in Table I11 would be totally inhibited at 0.10 per cent and some of them as low as 0.010 per cent of this preservative. It is interesting to note that the dry-rot fungi which showed sharply acid to methyl orange were also very sensitive to zinc meta-arsenite. of Powdered Zinc Meta-Arsenite toward Various Funei ‘URE AND CONCENTRATION OF Zn(As0z)z IN CULT FUNGUS GROWTHO F FUNGUS 0.00% 0 . 3 0 % 0.10% 0.06% 0.02% Fomes annosus None Feeble Moderate Good Moderate Good h’one Feeble Feeble Polyphorus anceps Polyphorus schumeinilzii None None Moderate Good Good Feeble Feeble &-one None Poria incrassala Moderate Good None Feeble Feeble Poria subacida Good None Feeble Moderate Good Steveum subpilealum Good None None None Trametes p i n i Good None None Feeble Polyphorus befulinus h’one Feeble Moderate Good Polysficlus versicolor Good None None None Coniophora cerebella Good h-one Moderate Feeble Merulius lachrymans Good Daedalia qucrcina None None Feeble Feeble Good None Feeble Moderate Good Lenziles lrabea Polyphorus sulphureus None Feeble
creosoted wood completely inhibited Fomes annosw and 4.49 grams of wood treated with zinc meta-arsenite also prevented growth of the fungus. The creosoted wood had been originally impregnated with 419 kg. per cubic meter (27 pounds per cubic foot) of grade No. 1 creosote while the wood containing zinc meta-arsenite was treated with 10.5 kg. per cubic meter (0.66 pound per cubic foot) of that preservative. It seemed desirable to test the resistance of the weathered wood containing zinc meta-arsenite against other fungi; therefore additional cultures of this type were prepared. The cultures contained 1.301, 2.784,4.488, and 6.570 grams of wood with enough agar-malt sirup gel to make the total weight 20 grams. These contained, in the wood, 0.1, 0.2, 0.3, and 0.4 per cent zinc meta-arsenite based on the total weight of the culture. The cultures were next inoculated with the fungi under test. Table I V lists the fungi and the results of the test. It shows that wood containing zinc meta-arsenite which has been cut into small pieces and exposed to the weather for 10 months has very high resistance to every one of this collection of rotproducing organisms. The wood is not only unattacked itself but is able to prevent fungous growth in the non-toxic nutrient gel with which i t is mixed. of W o o d Impregnated w i t h Zinc Meta-Arsenite toward Fungi CONCENTRATION OF Zn(As0dz AND GROWTH OF FUNGUS FUNGUS 0.4% 0.2% 0.1% 0.0% None Feeble Fomes annosus Feeble Good None Feeble Feeble Good Polyphorus anceps None None Polyphorus schweinilzii None Good Poria incrassata None Feeble None Good Poria subacida None None Feeble Good Slereum subpileotum None None Feeble Good Trametes pini None None Feeble Good Polyphorus belulinus None None None Good Polystictus versicolor None Feeble Feeble Gocd None Feeble Good ConioDhota cerebella None None None None Merulius lachrymans Good Daedalia quercino None None Good Good Ncne Feeble Good Lenziley lrabea hTone None None Good Polyphorus sulphureus None
Table IV-Toxicity
A Cheap and Accurate Metal Scale for Scientific Instruments’ David Crowther and J. J. Willaman UNIVERSITY OF MINNESOTA, ST. PAUL, MI“.
Table 111-Toxicity
I
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-
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I n a previous paper of this series4 toxicity tests are described in which wood impregnated with various preservatives is finely ground, mixed with nutrient gel, and inoculated with a fungus. It was found, with sawdust made from treated wood which had been exposed in small pieces to the action of the weather for 10 months, that the zinc meta-arsenite retained its high toxicity while creosoted wood had lost most of its toxicity and zinc chloride-treated wood actually permitted fungous attack. For example, 20-gram cultures containing 4.51 grams of 2 n d . Eng. Chem., 19,1343 ( 1 9 2 7 ) .
Vol. 20, No. 1
HE writers recently had occasion to alter the scale on a color grader used for honey and sirups. The method adopted was to make a “positive” zinc etching of the desired scale and attach it to the instrument in place of the original. The scheme apparently should have wide application and, although the idea undoubtedly is not new, it does not appear to be generally known. An ink drawing is made two or three times as large a s the desired scale. The drawing is sent to the print shop with instructions as to the exact size of the reproduced scale. Instead of the usual reversed etching, a “positive” is made. The characters of the scale stand out in relief, the accuracy is the same as the original drawing, the scale is durable, and the cost is negligible compared with an etching or an engraved scale. 1
Received November 21, 1927. ~
Calendar of Meetings American Chemical Society-75th Meeting, St. Louis, Mo., April 16 to 20, 1928. American Electrochemical Society-Hotel Stratfield, Bridgeport, Conn., April 26 to 28, 1928.
