WAT 
WAT 
89a WAT 
ease the precipitate, which consists both 
of lime and magnesia, is to be dissolved 
in sulphuric acid, evaporated to dryness, 
and is to be treated with twice its weight 
of cold water; which dissolves the sul- 
phat of magnesia, and leaves the other 
salt. Let the sulphat of magnesia be eva- 
porated to dryness, exposed to a heat of 400° 
and weighed. The same process succeeds 
if alum is present instead of sulphat of lime. 
The precipitate in that case, previously 
dried, is to be treated with acetic acid, which 
dissolves the magnesia and leaves the alumi- 
na. The magnesia may be again precipi- 
tated, dried, and weighed. If sulphat of iron 
is present, it may be separated by exposing 
the water to the air for some days, and mix- 
ing with it a portion of alumina. Both the 
oxide of iron and the sulphat of alumina thus 
formed, precipitate in the state of an inso- 
luble powder. The sulphat of magnesia may 
then be estimated by the rules above ex- 
plained. 
5. Sulphat of iron may be estimated by 
precipitating the iron by means of prussic 
alkali, having previously determined the 
weight of the precipitate produced by the 
prussiat in a solution of a given weight of sul- 
phat of iron in water. If muriat of iron is 
also present, which is a very rare case, it 
may be separated by evaporating the water 
to dryness, treating the residuum with alco- 
hol, which dissolves the muriat, and leaves 
the sulphat. Or the sulphat may be esti- 
mated with great precision by the rules laid 
down by Mr. Kirwan. 
V. Let us now consider the method of es- 
timating the quantity of the different muriats 
which may exist in waters. 
If muriat of potass or of soda, without any 
other salt, exists in the water, we have only to 
decompose them by nitrat of silver, and dry 
the precipitate ; for 217.65 of muriat of silver 
indicate one hundred of muriat of potass, and 
two hundred and thirty-five of muriat of silver 
indicate one hundred of common salt. 
The same process is to be followed if the 
alkaline carbonats are present ; only these 
carbonats must be previously saturated with 
sulphuric acid, and we must precipitate the 
muriatic acid by means of sulphat of silver 
instead of nitrat. The presence of sulphat 
of soda does not injure the success of this 
process. 
If muriat of ammonia accompanies either 
of the fixed alkaline sulphats without the 
presence of any other salt, decompose the 
sal ammoniac by barytes-water, expel the 
ammonia by boiling, precipitatcthe barytes by 
diluted sulphuric acid, and saturate the muri- 
atic acid with soda. The sulphat of barvtes 
thus precipitated indicates the quantity of 
muriat of ammonia; one hundred grains of 
sulphur indicating 49.09 grains of that salt. 
If sulphats are present in the solution, they 
ought to he previously separated. 
If common salt is accompanied by muriat 
of lime, muriat of magnesia, muriat of alu- 
mina, or muriat of iron, or by all of these to- 
gether without any other salts, the earths 
may be precipitated by barytes-water, and 
redissolved in muriatic acid. They are then 
to be separated from each other by the rules 
formerly laid down ; and their weight being 
determined indicates the quantity of every 
particular earthy muriat contained in the 
water. For fifty grains of lime indicate one 
hundred of dried muriat of lime ; thirty 
grains of magnesia indicate one hundred of 
the muriat of the earth ; and 21.8 grains of 
alumina indicate one hundred of the muriat 
of alumina. The barytes is to be separated 
from the solution by sulphuric acid, and the 
muriatic acid expelled by heat, or saturated 
with soda ; the common salt may then be 
ascertained by evaporation, subtracting in the 
last case the proportion of common salt indi- 
cated by the known quantity of muriatic acid 
from which the earths had been separated. 
When sulphats and muriats exist together, 
they ought to be separated either by pre- 
cipitating the sulphats by means of alcohol, 
or by evaporating the whole to dryness, and 
dissolving the earthy muriats in alcohol. 
The salts thus separated may be estimated by 
the rules already laid down. 
When alkaline and earthy muriats and 
sulphat of lime occur together, this last salt is 
to be decomposed by means of muriat of 
barytes. The precipitate ascertains the weight 
of sulphat of lime contained in the water. 
The estimation is then to be conducted as 
when nothing but muriats are present ; only 
from the muriat of lime that proportion of 
muriat must be deducted which is known to 
have been formed by the infusion of the mu- 
riat of barytes. 
When muriats of soda, magnesia, and alu- 
mina, are present together with sulphats of 
lime and magnesia, the water to be examined 
ought to be divided into two equal portions. 
To the one portion add carbonat of mag- 
nesia till the whole of the lime and alumina 
is precipitated. Ascertain the quautity of 
lime which gives the proportion of sulphat of 
lime. Precipitate the sulphuric acid by mu- 
riat of barytes. This gives the quantity con- 
tained in the sulphat of magnesia and sulphat 
of lime ; subtracting this last portion, we have 
the quantity of sulphat of magnesia. 
From the second portion of water precipi- 
tate all the magnesia and alumina by means 
of lime-water. The weight of these earths 
enables us to ascertain the weight of mu- 
riat of magnesia and of alumina contain- 
ed in the water, subtracting that part of the 
magnesia which existed in the state of sul- 
phat, as indicated by the examination of the 
first portion of water. After this estimation 
precipitate the sulphuric acid by barytes 
water, and the lime by carbonic acid. The 
liquid evaporated to dryness leaves the com- 
mon salt. 
VI. It now only remains to explain the 
method of ascertaining the proportion of the 
nitrats which may exist in waters. 
1. When nitre accompanies sulphats and 
muriats without any other nitrat, the sulphats 
are to be decomposed by acetat of barytes, 
and the muriats by acetat of silver. The 
water after filtration, is to be evaporated to 
dryness, and the residuum treated with alco- 
hol, wiiich dissolves the acetats, and leaves 
the nitre ; the quantity of which may be 
easily estimated. If an alkali is present, it 
ought to be previously saturated with sulphur- 
ic or muriatic acid. 
2. If nitre, common salt, nitrat of lime, and 
muriat of lime or of magnesia, are present 
together, the water ought to be evaporated to 
dryness, and the dry mass treated with alco- ( 
hoi, which takes up the earthy salts. From 
the residuum, redissolved in water, the nitre 
may be separated, as estimated as in the last 
case. The alcohol solution is to be evapor- 
ated to dryness, and the residuum redissolved 
in water. Let us suppose it to contain muriat 
of magnesia, nitrat of lime, and muriat of 
lime. Precipitate the muriatic acid by nitrat 
of silver, which gives the proportion of' muriat 
of magnesia and of lime. Separate the 
magnesia by means of carbonat of lime, and 
note its quantity. This gives us the quantity 
of muriat of magnesia. And subtracting the 
muriatic acid contained in that salt from the 
whole acid indicated by the precipitate of 
silver, we have the proportion of muriat of 
lime. Lastly, saturate the lime added to pre- 
cipitate the magnesia with nitric acid. Then 
precipitate the Whole of the lime by sulphuric 
acid ; and subtracting from the whole of the 
sulphat thus formed that portion formed by 
the carbonat of lime added, and by the lime 
contained in the muriat, the residuum gives 
us the lime contained in the original nitrat ; 
and 35 grains of lime form 100 of dry nitrat 
of lime. 
Water-sea. See Sea. 
WA1 ER-COLOURS. Painting in water- 
colours, is an art capable of affording the 
highest delight to the eye, since no mode of 
representation can display the appearances 
of nature with greater splendour. It is an 
art which has of late been carried forward 
with unprecedented success, and may be said 
at present to be the most perfect species of 
design or painting, which is in practice 
amongst our artists. To this the facility of 
the materials employed in it, contributes in 
no small degree. It is not attended with the 
embarrassments to which oil-painting, or most 
other kinds of painting, are liable, but pro- 
ceeds by ready and uninterrupted progress 
to the completion of its task. 
Tbs preliminary parts of study requisite 
for the young student in the attainment of 
this art, have been treated at large under the 
article of drawing. See Drawtng. We 
can recommend no more advantageous me- 
thod for his farther progress, than the care- 
fully studying and copying the various works 
of excellence by the hands of the best mas- 
ters, until he shall be able to follow, if not to 
rival them, in the imitation of nature. We . 
shall now endeavour to furnish him with the 
best means for this purpose, by describing the 
colours which are employed in washing, and 
by giving the most approved directions for 
preparing and using them. 
The materials and implements necessary 
for the practice of water-colours (or washing, 
as it is sometimes called) are, — gum-colours, 
of which we shall treat hereafter more par- 
ticularly ; camels’-hair pencils, fitches, a pal- 
lette, and penknife. 
The general or simple colours, and the 
various species of each, fit for- painting jp 
water-colours, are as follow : 
Whites. 
Ceruse 
Constant white 
White lead 
Spanish white 
Flake white 
Spodium 
Browns. 
Spanish brown 
Spanish liquorice 
Umber 
Bistre 
Burnt Terra de Sia**» 
na 
Unburnt ditto 
