The Acidimeter And Its Use

"The first instrument of this kind which came into general use, was one

invented by DR. OTTO, and consists of a glass tube, from ten to twelve

inches in length, half an inch in width, and closed at the lower end.

Fig. 33 shows OTTO'S Acidimeter.



"The tube is filled to the partition line _a_, with tincture of litmus.

The must to be examined, before it has begun to ferment is then poured

into the tube, unti it reaches the line 0. The blue tincture of

litmus, which would still be blue, if water had been added, is turned

into rose-color by the action of the acids contained in the must.



"If a solution of 1,369 per cent, of caustic ammonia is added to this

red fluid, and the tube is turned around to effect the necessary

mixture, keeping its mouth closed with the thumb, after the addition of

more or less of the ammonical fluid, it will change into violet. This

tinge indicates the saturation of the acids, and the height of the

fluid in the tube now shows the quantity of acid in the must, by whole,

half and fourth parts per cent. The lines marked 1, 2, 3, 4, indicate

whole per cents.; the short intermediate lines, one-fourth per cents."



When DR. GALL, shortly before the vintage of 1850, first publicly

recommended the dilution of the acids, he was obliged to refer to this

instrument, as already known, and everywhere at hand, which was at the

same time cheap, and simple in its use. "It is true, however, that if

must is examined by this instrument, the quantity of acids contained in

it, is really somewhat larger than indicated by the instrument; because

the acids contained in the must require for their saturation a weaker

solution of ammonia than acetic acid." As however, OTTO'S acidimeter

shows about one eighth of the acids less than the must actually

contains, and about as much acids combined with earths is removed

during fermentation, DR. GALL recommends that the quantity of acids be

reduced to 6-1/2, or at most 7 thousandths of OTTO'S acidimeter, and

the results have shown that this was about the right proportion; as the

wines in which the acids were thus diluted were in favor with all

consumers.



"The acidimeter referred to was afterwards improved, by making the tube

longer and more narrow, and dividing it into tenths of per cents,

instead of fourths; thus dividing the whole above 0 into thousandths.

But although by this improved acidimeter the quantity of acids could be

ascertained with more nicety, there remained one defect, that in often

turning the glass tube for mixing the fluids, some of the contents

adhered to the thumb in closing its mouth. This defect was remedied in

a new acidimeter, invented by Mr. GEISLER, who also invented the new

vaporimeter for the determination of the quantity of alcohol contained

in wine. It is based on the same principle as OTTO'S, but differs

altogether in its construction. It is composed of three parts, all made

of glass; the mixing bottle, Fig. 34; the Pipette, Fig. 35; and the

burette, Fig 36. Besides, there should be ready three small

glasses--one filled with tincture of litmus, the second with a solution

of 1,369 per ammonia, and the third with the must or wine to be tested;

also, a taller glass, or vessel, having its bottom covered with cotton,

in which glass the burette, after it has been filled with the solution

of ammonia, is to be placed in an upright position until wanted.



"To use this instrument the must and the tincture of litmus, having

first received the normal temperature of 14 deg. Reaumer, are brought into

the mixing bottle by means of the pipette, which is a hollow tube of

glass, open on both ends. To fill it, place its lower end into the

tincture or must, apply the mouth to the upper end, and by means of

suction fill it with the tincture of litmus to above the line indicated

at A. The opening of the top is then quickly closed with the thumb; by

alternately raising the thumb, and pressing it down again, so much of

the tincture is then allowed to flow back into the glass so as to lower

the fluid to the line indicated at A. The remainder is then brought

into the bottle, and the last drops forced out by blowing into the

pipette.



"In filling it with must, raise the fluid in the same way, until it

comes up to the line indicated at B, and then empty into the mixing

bottle.



"The burette consists of two hollow tubes of glass. In filling it, hold

the smaller tube with the right hand into the glass containing the

solution of ammonia, apply the mouth to the larger one, and by drawing

in the fluid the tube is filled exactly to the line indicated at 0 of

the tube.



"Holding the mixing bottle by the neck between the thumb and forefinger

of the left hand, place the smaller tube of the burette into the mouth

of the mixing bottle, which must be constantly shaken; let enough of

the solution of ammonia be brought drop by drop, into the mixture in

the bottle, till the red has been changed into the deep reddish blue of

the purple onion. This is the sign of the proper saturation of the

acids. To distinguish still better, turn the mixing bottle upside down,

by closing its mouth with the thumb, and examine the color of the fluid

in the tube-shaped neck of the bottle, and afterwards, should it be

required, add another drop of the ammonia. Repeat this until the proper

tone of color has been reached, neither red nor blue. After thus fixing

the precise point of the saturation of the acids, the burette is held

upright, and the quantity of the solution of ammonia consumed is

accurately determined,--that is, to what line on the scale the burette

has been emptied. The quantity of the solution so used corresponds with

the quantity of acids contained in the must--the larger division lines

opposite the numbers indicating the thousandths part, and the smaller

lines or dots the ten thousandths part.



"Until the eye has learned by practice to recognize the points of

saturation by the tone of color, it can be proven by means of litmus

paper. When the mixture in the bottle begins to turn blue, put in the

end of a slip of litmus paper about half an inch deep, and then draw

this end through your fingers, moistened with water. So long as the

ends of the blue litmus paper become more or less reddened, the acids

have not been completely saturated. Only when it remains blue, has the

point of saturation been reached.



"In examining _red_ must, the method should be modified as

follows:--Instead of first filling the pipette with tincture of litmus,

fill it with water to the line A, and transfer it into the bottle.

After the quantity of must has been added, drop six-thousandths of the

solution of ammonia into the mixture, constantly shaking it while

dropping, then test it, and so on, until, after every further addition

required with litmus paper, it is no longer reddened after having been

wiped off."



DR. GALL further gives the following directions, as a guide, to

distinguish and determine the proportion of acids which a must should

contain, to be still agreeable to the palate, and good:



"Chemists distinguish the acid contained in the grape as the vinous,

malic, grape, citric, tannic, gelatinous and para-citric acids. Whether

all these are contained in the must, or which of them, is of small

moment for us to know. For the practical wine-maker, it is sufficient

to know, with full certainty, that, as the grape ripens, while the

proportion of sugar increases, the quantity of acids continually

diminishes; and hence, by leaving the grapes on the vines as long as

possible, we have a double means of improving their products--the must

or wine.



"All wines, without exception, to be of good and of agreeable taste,

must contain from 4-1/2 to 7 thousandths parts of free acids, and each

must containing more than seven thousandths parts of free acids may be

considered as having too little water and sugar in proportion to its

quantity of acids.



"In all wine-growing countries of Germany, for a number of years past,

experience has proved that a corresponding addition of sugar and water

is the means of converting the sourest must, not only into a good

drinkable wine, but also into as good a wine as can be produced in

favorable years, _except_ in that peculiar and delicate aroma found

only in the must of well-ripened grapes, and which must and will always

distinguish the wines made in the best seasons from those made in poor

seasons.



"The saccharometer and acidimeter, properly used, will give us the

exact knowledge of what the must contains, and what it lacks; and we

have the means at hand, by adding water, to reduce the acids to their

proper proportion; and by adding sugar, to increase the amount of sugar

the must should contain; in other words, we can change the poor must of

indifferent seasons into the normal must of the best seasons in

_everything_, _except_ its bouquet or aroma, thereby converting an

unwholesome and disagreeable drink into an agreeable and healthy one."