Jökull - 01.01.2001, Page 80

S. P. van Swinden
as proven by the discoloring produced by its action on
the colors and the way the discoloring occurred. M.
du Vasquier showed many people some canvas with
red violet and black colors. Half of the canvas was
immersed in diluted hydrochloric (vitriolic) acid and
showed similar alterations than the paintings exposed
to the fog last summer; he noticed that on the can-
vas, the red became orange, violet became pale yel-
low and black was washed away. When washed with
water these samples looked similar to those we found
on the paintings that were exposed to the fog and later
washed with water. No painted canvas manufacturer
in this country could bring back the vivacity of the
color and they all noticed with M. du Vasquier that
acid or alkali treatments even worsen the painting.
M. du Vasquier assured me that only acids could
cause these effects with more or less intensity. He
used very caustic alkali on the paintings and showed
that the red color became violet without orange stage
and, that if washed and left in the sun for few days,
the red color reappeared. He tried other samples with
strong alkali such as “foye de soufre volatil, rectified
wine spirit, huiles grasses, huiles etherees” and none
of these produced similar effects that those observed
using acid solutions.
M. du Vasquier noticed that the different acids
have different degree of effect, for example nitric and
sulfuric acids have a stronger effect than tartre and se-
lenite”.
These observations leave no doubt, but that this
haze united some acid, or rather some acid gas. This
gas was not deeply and chemically mixed; it appeared
heavier than the atmospheric air, since it occupied the
lower region of the atmosphere; finally that it drove
itself into designs, while it mixed itself with water27,
which wholly agrees with what Dr. Brugmannusn ob-
served; that the vapor of burning sulfur did not go into
the leaves, unless after the vapor had been mixed with
watery vapor. The acidity, weight, and effects of this
gas, bring it about that, as I believe, it approached
the nature of that gas which is called AER–ACIDUS–
VITROLICUS.28
For the weight of this gas is greater than that of air,
its affinity with water, the volatile odor of sulfurous
acid; the cough which it provokes, the effect which
it causes in metal, especially when mixed with wa-
ter, are properties and effects similar to those, which
the haze exhibited, as is established from those things
which we spoke of above. More about the nature of
this haze I cannot bring to light.
I shall add, that very great heat followed this haze
for the whole month of July, especially on the 28
 ,
when the thermometer showed 26 3/4 degrees [Réau-
mur]; that the medium heat of the month was 18.2 ,
which surpasses all examples which had ever been
recorded in these regions; a great dryness appeared
then from 21 June to 21 July, in which time no rain
fell; finally on days 2, 3, and 4 of August again there
was very great heat, that is to say on day 2 to 26.9 ,
on day 3 to 23.3 , on day 4 to 19.2 , and in August
we had 12 cloudy days. Indeed the haze was light, but
here [in Franeker] a great number [of clouds] were
never, as far as I know, observed. For in Septem-
ber there were many clouds, and in each month much
stronger thunder, which produced various disasters,
and much damage.


This could be regarded as the earliest reference to formation of sulfuric aerosols.

The meaning of this term is unclear.
80 JÖKULL No. 50