206 
DR. GLADSTONE ON CIRCUMSTANCES MODIFYING 
Copper salts. 
Soluble copper salts are, I believe, all of a blue colour when dissolved in a large 
amount of water; but a strong solution of the chloride, and of one or two others, is 
green. It has frequently been observed, that on the addition of strong hydrochloric 
acid to a concentrated solution of sulphate of copper, a green colour takes the place 
of blue ; and it has been naturally concluded that chloride of copper was then formed. 
This reaction was likewise investigated. 
A solution of sulphate of copper was made, containing 125 grm. of the crystals in 
1000 gr. measures of water. Hydrochloric acid was taken, having a specific gravity 
of 1139 at 58° F., and therefore containing 28 per cent, of real acid. Hence, as may 
be easily calculated, equal bulks of the hydrochloric acid and sulphate of copper 
solutions represent eight equivalents of the former to one of the latter. A number of 
equal portions of the blue salt were mixed with respectively one-eighth, one-quarter, 
one-half, &c. of their volume of the hydrochloric acid in a series of glass tubes of the 
same size. The following colours resulted : — 
Sulphate Hydrochloric 
of copper. acid. 
Colour of mixture. 
1 equiv.-l- 1 equiv. 
Blue. 
1 equiv.-f- 2 equivs. 
Blue with a tinge of green. 
1 equiv. q- 3 equivs. 
Dull green. 
1 equiv.-f 4 equivs. 
Dull green. 
1 equiv.-f 6 equivs. 
Bright green. 
1 equiv.-f 8 equivs. 
Bright green. 
1 equiv.-f 16 equivs. 
Very bright green. 
The tint designated as “ bright green ” is of a very vivid hue, in which yellow seemed 
to preponderate : it arises from the formation of a hydrochlorate of the chloride of 
copper. 
From this it is evident that single equivalents of sulphate of copper and of hydro- 
chloric acid are not resolved wholly (nor indeed to any great extent) into chloride 
of copper and sulphuric acid ; and that the relative mass of the two substances in- 
fluences the result. 
In order to observe the influence of the mass of water, the following experiments 
were instituted. Eight portions were taken of a saturated solution of sulphate of 
copper at 60° F., and were mixed with progressively increasing amounts of the hydro- 
chloric acid solution. The colours produced were noted. They are given in column I. 
of the subjoined table. Each of the mixtures was then diluted with half its volume 
of water. The resulting shades are given in column II. Column HI. represents the 
shades when the water was doubled ; column IV. when the solutions were of three 
times their original volume; — 
