=+and the independent variables x1 5 hydrogen peroxide

(% by weight), x2 5 sodium hydroxide (% by weight), x3 5 silicate (% by weight), and x4 5 process temperature

(“Advantages of CE-HDP Bleaching for High Brightness Kraft Pulp Production,” TAPPI [1964]: 107A–173A).

1 .492x5 yˆ 5 2151.36 2 16.22x1 1 13.48x2 1 .094x3 2 .253x4 12.39 1 6.67x1 2 15.25x2 yˆ 5 x1 x2 x3 x4 y

.2 .2 1.5 145 83.9

.4 .2 1.5 145 84.9

.2 .4 1.5 145 83.4

.4 .4 1.5 145 84.2

.2 .2 3.5 145 83.8

.4 .2 3.5 145 84.7

.2 .4 3.5 145 84.0

.4 .4 3.5 145 84.8

.2 .2 1.5 175 84.5

.4 .2 1.5 175 86.0

.2 .4 1.5 175 82.6

.4 .4 1.5 175 85.1

.2 .2 3.5 175 84.5

.4 .2 3.5 175 86.0

.2 .4 3.5 175 84.0

.4 .4 3.5 175 85.4

.1 .3 2.5 160 82.9

.5 .3 2.5 160 85.5

.3 .1 2.5 160 85.2

.3 .5 2.5 160 84.5

.3 .3 0.5 160 84.7

.3 .3 4.5 160 85.0

.3 .3 2.5 130 84.9

.3 .3 2.5 190 84.0

.3 .3 2.5 160 84.5

.3 .3 2.5 160 84.7

.3 .3 2.5 160 84.6

.3 .3 2.5 160 84.9

.3 .3 2.5 160 84.9

.3 .3 2.5 160 84.5

.3 .3 2.5 160 84.6