TECHNICAL NO T E__ number 163 
 
 FOREST PRODUCTS LABORATORY UNITED STATES Fp^ST SERVICE 
 
 MADISON 5. WISCONSIN REVISED JUnI 19^9 
 
 ATLANTA, ( ' **'* 
 
 DETERMINING FENETKATICW OF WOOD PRESERVATIVES 
 
 U.S. DEPOSITORY 
 The effectiveness of any wood preservative treatment 
 
 is 
 
 measured very largely by the depth to which the preservative 
 penetrates. Thi6 can be determined by the following tests, 
 which are used by the Forest Products Laboratory. 
 
 The presence of creosote, creosote mixtures, or other 
 dark -colored oils is indicated by the dark discoloration, 
 and the degree of penetration may readily be determined by 
 taking a sample at a point free from checks and other imper- 
 fections and at a considerable distance from the end of the 
 stick. This may be done either with an ordinary l/2-inch 
 bit, and measuring the penetration on the wall of the hole, 
 or with an increment borer, which brings out a core of wood 
 that shows in cross section the depth of penetration and is 
 easily examined. The observation should be made at once, 
 because the oil spreads rapidly over the cut surface, par- 
 ticularly over the end-grain of the wood. With low -viscosity 
 oils it is often desirable to examine a tangential or radial 
 section of the treated wood rather than an end-grain section. 
 In order to prevent infection, the hole in the treated piece 
 should be tightly closed with a thoroughly treated plug. 
 
 No reliable method has been found far determining the 
 depth of penetration of pentachlorophenol when used in 
 colorless or light-colored oil solvents. In boring cores 
 from wood recently treated, however, it is often possible to 
 distinguish the "wet" treated portion from the untreated 
 portion of the boring. 
 
 As zinc chloride is colorless, the depth of penetration 
 of this preservative must be ascertained by chemical means. 
 The most common method of determining penetration an a cut 
 face or boring consists in spraying over the freshly cut 
 surface a mixture of equal parts of a 1 percent potassium 
 ferricyanide solution, a 1 percent potassium Iodide solution, 
 and a 5 percent solution of soluble starch. This colors the 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 09216 6932 
 
 treated portion a very aark blue, out does not affect the 
 untreated wood. Although the color fades in time, "may 
 he brought back by spraying again. This method may also be 
 used on chromated zinc chloride. 
 
 Sodium fluoride is colorless, but its presence in wood 
 can be determined by the following method. Make one solu- 
 tion (1) in the ratio of 5 grams of zirconium oxychloride 
 In 500 cc. of water. Make another solution (2) in the 
 ratio of 2 grams of sodium alizarine sulfonate, kO cc. of 
 concentrated hydrochloric acid, and U60 cc. of water. The 
 two solutions are kept separated until ready for use, when 
 a quantity of solution 2 is added to an equal quantity of 
 solution 1. It is essential that 2 be added to 1 rather 
 than vice versa. The cut surfaces or borings are sprayed 
 or dipped in the solution. The treated wood will turn 
 yellow while the untreated wood will remain dark red. This 
 method is also recommended by the proprietors of some 
 patented fluoride-phenol-dichromate preservatives to meas- 
 ure the penetration of the sodium fluoride. 
 
 Mercuric chloride is also colorless, but dipping the 
 wood in a solution of hydrogen sulfide turns the treated 
 area black. 
 
 The penetration of preservatives containing copper 
 salts, such as Greensalt (Erdalith or Ascu), Celcure, and 
 Chemonite, can usually be observed without the aid of 
 special stain. The following stein has been found useful, 
 ^ever, for determining the penetration of these Preserva- 
 tives: Dissolve 0.5 gram 5-diphenyl carbazide In 50 ml. of 
 isopropyl alcohol and 50 ml. of water. When a boring or 
 crosHLtion of treated wood is sprayed or di pped in this 
 solution, the presence of the copper compound is indicated 
 by a purple color while the untreated wood shows little 
 change. 
 
 As individual pieces may show an abnormally high or 
 low degree of penetration, a sufficient number of tests 
 shoula^e made to obtain a fair average. Samples should 
 be taken at a considerable distance from the ends of the 
 stick" ^ order that they will not be affected by the heavy 
 longitudinal penetration from the ends. 
 
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