THE WOODS OF THE UNITED STATES. 



265 



wood may be determined by microscopic examination of its structure ; that is, two specimens of the wood of any 

 species to which the census tests have been applied being given, their relative values can be determined by an 

 examination of their structure as well as or better than by any elaborate experiments. 



/ 



n ' 



TAKNDT VALUES. 



The amount of tannin contained in the bark of various trees of the United States has been determined. 



These determinations give the proportion of tannin. They do not indicate the real value of the bark of the 

 species for tanning, which can only be obtained by actual experiments made on a large scale, other properties in 

 the bark, beside the percentage of tannin, affecting the value of the leather prepared with it. 



These determinations must therefore be regarded as approximations, which will serve, in some cases, to 

 indicate species not now in general use for th^s purpose, which may be looked to as possible sources of tannin 

 supply. 



The methods adopted by Mr. Sharpies in making these determinations are described by him as follows : 



The tannin in each case was determined in the rossed bark ; that is, bark deprived of the main part of the outside coating. The 

 method employed was that devised by Lowenthal, which may be thus briefly described: A standard decoction of the bark is titrated 

 with permanganate of potash, a quantity of indigo being first added to it. In a second portion the tannin is precipitated by means of 

 gelatine, and the gallic acid in the liquid again determined by permanganate and indigo. The difference between these two readings 

 gives the amount of tannin in the bark, the value of the permanganate having previously been determined by pure tannic acid, or by 

 oxalic acid and calculation. 



The bark of the following species has been examined : 



140 

 160 

 251 



2se 



280 



261 



281 

 27 

 289 

 272 

 274 



Botanical name. 



Gordonia Laaianthna . 

 Proeopis Jnliflora 



Bhizophora Mangle 



Exoatemma Caribtenm . 



QaeTcosalba 



Qnerona maorooarpa... 



Qnercna Prhras 



Qaercna prinoidea (old tree). . . 



Qaercaa prinoidea (yoong tree) 



Quercna vlrena 



Qnercna Emoryl 



Qnercna mbra 



Qnercna tinotoria 



Common name. 



Loblolly Bay. Tan Bay , 



Ueaqnit. Algaroba. Honey 



Locnat Honey Pod. 

 Mangrove 



WUteOak 



Bnrr Oak. Mo8syK>np Oak. 



Over-cnp Oak. 

 Clieetnnt Oak. Book Cheet- 



nat Oak. 

 Yellow Oak. Cbestnat Oak. 



Chinquapin Oak. 



do 



Live Oak 



Black Oak 



Bed Oak. Black Oak 



Black Oak. Yellow-bark Oak. 



QnercitronOak. Yellow Oak. 



13.14 

 4.04 



31.04 

 S.81 

 B.99 

 4.50 



6.25 



4.33 



10.33 

 10. 4 

 0.76 

 4.56 

 S.90 



2.3S 

 8.71 



6.70 

 7.16 

 6.11 

 &05 



3.83 



6.23 

 8.69 

 16.09 

 4.43 

 5.73 



275 

 276 

 277 

 287 



290 



Botanical name. 



Qnercna Kelloggii . 



Qnercna nigra 



Qnercna falcata 



Qnercna densiflora. 



Caataneavnlgaria, var. Ameri- 

 cana. 



Ficea nigra 



Picea Engelmanni 



Pioea Engelmanni 



Plcea Engelmanni 



Tanga Canadenaia 



Tsnga Mertensiana 



Tanga Mertensiana 



Tanga Pattoniana 



Paendotenga Donglasii 



Common name. 



Black Oak 



Block Jack. Jack Oak 



Spaniab Oak. Bed Oak 



TanbarkOak. CheetnntOak. 



Peach Oak. 

 Cheetnnt 



Black Spruce.. 

 White Spmce. 



...do , 



...do 



Hemlock 



...do 



...do 



Bed Fir. YeUow Fir. Ore- 

 gon Pine. Douglas Mr. 



6.76 



4.36 



8.59 



16.46 



6.25 



7.20 

 20.56 

 17.01 



izeo 



13.11 

 14.42 

 15.87 

 15.72 

 13.79 



8.64 

 6.28 

 4.32 

 8.84 



2.00 



2.84 

 2.75 

 2.32 

 0.75 

 1.31 

 1.44 

 1.49 

 2.48 

 1.56 



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