FISH-FET PRESERVATIVES. 



67 



The only lines that at any time make a higher score than white line 

 are the line, M, treated with copper oleate, after the first and second 

 month, and P, another line treated with copper oleate, after the first 

 month. The Dutch method, L, makes a good score. The copper 

 paints, Q and R, at first make a poor showing because of excessive 

 weight and low wearing ability, but because of a good preserving 

 effect they occupy a high place, compared with others, after three 

 months. "The tarred lines, F, G, and H, all make similar scores but 

 are intermediate between the better and poorer preservatives. In 

 Figure 35 these lines are grouped for a more convenient interpretation. 



320 

 300 

 280 

 260 

 240 



220 

 200 

 180 



v,l60 



»- 

 z 



oMO 



z 



-jl20 

 a: 



o 



i'^lOO 



eo 

 eo 



40 



20 







>;Q 



12 3 4 



NUMBU OF MONTHS mOSiD 



Fig. 35.— Scores of the presen-atives shown in Figure 34, with the preservatives 

 ha^ing a similar effect grouped. 



The samples treated with copper oleate easily lead as all-roimd 

 preservatives when rated by the method described, the copper paints 

 and the Dutch method show merit, the tarred samples are somewhat 

 better than nothing, and the quercitron and potassium bichromate 

 method and three proprietary preservatives do not score at any point 

 as high as the plam white line. 



The striking fact, already mentioned, is again evident in this con- 

 nection, that those preservatives that contam copper in some form 

 deposited in the lines are best — copper oleate, the copper paints, and 

 the Dutch method. It is plain that in the Dutch method copper is 

 the active ingredient, for in the quercitron and potassium bichromate 

 method the same tanning extract mordanted without copper is ineffec- 

 tive. Since copper seems essential in a net preservative, the form that 



