Friday, 13 April 2018

The Salts of Brewing Waters (part three)

It's the final part of this series of posts on brewing water.

This time were looking at what to do if your water contains minerals detrimental to brewing. I'm tempted to say: get different water, bit obviously that isn't always practical.

"It may happen, however, that a brewer is not blessed either with a perfect water or with one which simply requires bringing up to Burton standard by increasing its salts, but has to produce good beers with a water containing salts altogether undesirable or even injurious to beer.production.

Sodium carbonate, if present to any great extent, would prove fatal to the brewing of anything but black beers, and sodium sulphate, though by no means as harmful, is nevertheless an undesirable constituent of brewing-waters.

For the decomposition of sodium carbonate the employment of free acid would be, to say the least, dangerous. One method used is to gypsum the water, but this causes the formation of sodium sulphate, which when present in any amount is most undesirable, although not so productive of harm as the car bonate. The sodium sulphate is therefore then decomposed by the addition of calcium chloride, yielding salt and calcium sulphate. By far the best method is the direct employment of calcium chloride solution, which at one operation decomposes both these sodium salts, calcium carbonate being precipitated and the much-desired calcium sulphate obtained in solution. The solution of calcium chloride must be pure and of a known strength, and the volume added to a water to be treated should contain an amount of the salt equivalent or rather more than equivalent to the sodium sulphate and carbonate. The methods employed in making an analysis of the solid matter dissolved in water are so well known that they require but little comment from me. There are, however, just a few points to which I should like to direct your attention.

Firstly, temperature at which the total solids should be dried. I believe the most usual temperature is 110° to 120°C., and when such is the case an allowance should be made in stating the salts present for the water of crystallisation of certain of them.

The following are given by a recognised authority on water analysis, for this temperature, although he admits that anomalous cases have occurred in which the salts appeared to have become anhydrous:

CaSO + 1/2 Aq. or {CASO4} + 1 Aq
MgSO4 + 1 Aq
Mg(NO2)2 + 2 Aq.
Ca(N03)2 + I Aq.

The method of estimating the soda and potash is, as you know, to evaporate firstly with barium hydrate to remove the sulphuric and carbonate acids, and then to treat with ammonium carbonate, to remove lime and magnesia. The filtrate obtained is evaporated to dryness with ammonium chloride, and the ammonium salts decomposed by gentle ignition. The sodium and potassium are then dissolved out with water. It is the method of ignition which should be noted, as it is of great importance. At first the heat must be gentle, and gradually increased until, when ammonium fumes ceased to be evolved, dull redness should be reached. If the heat be too rapidly raised, the alkaline chlorides melt, and appear to enclose some of the ammonium salts which are not completely removed, and the results are too high. Should the residue not be sufficiently heated, all the ammonium salts are not removed, and then too high a result is obtained. If heated to too high a temperature the alkaline chloride will partially volatilise and give t00 low a result. With practice very accurate results can be obtained. The potassium should always be estimated. It is not sufficient to estimate the alkalis as chloride and call the result sodium chloride, for in some waters an appreciable quantity of potassium is present. This can of course be estimated in the alkaline chlorides. The only other point to be noticed is the determination of nitrates and nitrites. Nitrites are not often present, but a careful determination of the nitrates should be made. The method is to evaporate the water under examination with potash, to get rid of ammonium salts, and then to reduce the nitrates by means of zinc-copper couple, ammonia being distilled off, after further addition of potash, and estimated by Nessler's reagent in the ordinary way. Now, the potash employed should be carefully looked into, for when ordinary potash is used the results obtained are generally too high, this being doubtless due to nitrates contained in the potash. It is a good plan to use potash precipitated by alcohol, but even then I have found a correction necessary. Wanklyn advises that the potash should be made by dissolving metallic potassium in water, but whether this is done or not a blank determination with the materials should certainly be made.

In conclusion, I am afraid my remarks have been for the greater part but old news. Still, in spite of that, they serve as an illustration of the direct application of chemistry to the improvement of a manufactured article, and on this ground may not be entirely devoid of interest."
The Brewers' Guardian 1893, pages 109 - 110.
The answer is chemistry. I would ask Andrew to explain to to me, but he's had his brain plugged into his gaming computer all day. Removing unwanted stuff is clearly more complicated than adding useful stuff.

Any ideas why Sodium carbonate and sodium sulphate are so bad for brewing? My guess is that it's something to do with the sodium.

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