The improvement in purifiers which were made of late, consist in making them considerably longer than heretofore, so that the carbonic acid will have to travel through a longer column of water, and consequently be better purified; another improvement consists in passing the carbonic acid through a series of purifiers, with one or two perforated plates (sieves) inserted, when the working is so much more effective.

In the American apparatus the gas is washed from one to three times before entering the cylinders. Purifiers or washers are either attached to the side of the generator, placed on the fountains or stand separately, according to the size and style of the plant.

Carbonated waters are liable to be tainted with the acid employed. This occurs where the gas is passed direct from the generator into the condenser without purification. When the gas is formed, a certain quantity of acid vapor always rises with it, and if this be not removed, it of course passes into and contaminates the water in the condenser. After the gas leaves the generator it enters a purifier, which is filled from half to two-thirds full of water, entering through a perforated diaphragm, placed at the bottom for the purpose of breaking and subdividing the gas bubbles, which would otherwise pass up through the water in large globules, a form by itself incompatible with thorough purification. One manufacturer places small chunks of marble (no marble dust, 9 which would clog the purifiers) in his washers, for the double purpose of dividing the gas into finer particles and absorbing any trace of sulphuric acid which might find its way over from the generator. It is claimed by this means that any traces of acid will unite with the marble, setting free additional gas, and indeed it fills the bill. If the first purifier is packed with small fragments of broken marble, and the interstices filled up two-thirds with water, it serves even three purposes: viz., washing and subdividing the gas and purifying it from traces of sulphuric acid. Instead of bubbling up through the water, which hardly checks the rapidity of the course of the carbonic gas, it is compelled to find its way slowly between the fragments, and is thus thoroughly divided and cooled as well as purified. Some gas, of course, is absorbed, but the quantity is very small. Fresh pieces of marble should be added as may be necessary from time to time, to keep the washer filled.

Another kind of apparatus has what are called gas domes and sediment traps, which serve to arrest any impurities from the generator before the gas enters the wet purifiers. These contrivances, as may be readily seen, are to thoroughly purify the gas before it enters the cylinders. Whatever plant is employed, the operator should be certain a sufficient quantity of water is always present in the washers, and it should be changed whenever opportunity serves and the purifiers previously rinsed, at least once every two or three days, better after every operation.

Instances are known where the carbonator has neglected filling his washers with water, and was unable to account for the peculiar taste of his beverages, when it was ascertained the purifiers were as dry as the desert of Sahara, and had been in that condition for no one knows how long. We have seen cases when the water in the gasometer vat or in purifiers was nearly stinking, and that the water had not been changed for many months. This is very bad management, and very culpable, for it is injurious to the consumers of the drinks so charged, as the water in vat or purifiers becomes so saturated with injurious and foul gas that it is not alone inefficient in cleansing the gas passed through it, but renders it very much more impure than it was originally.

Some are opposed to these ideas of the purification of gas, while others find one purifier amply sufficient to eliminate any impurities that are likely to pass. "Too much washing detracts from that sharpness and pungency which is the test of good carbonated waters," is asserted. The loss of gas in passing through several bodies of water is infinitesimal, and the number of washings absolutely necessary is only determined by the intelligence of the carbonator. Therefore to produce high class beverages, particular attention should be bestowed upon the generation and purification of the gas. Those of the manufacturers who have gone into the manufacture of a better and more delicate class of beverages, such as mineral waters, fine ginger ales, etc., have been obliged to look for some means or remedy to obtain pure carbonic acid, and there are undoubtedly some who were cautious enough in this particular respect, but their devices are unknown to the bottlers in general, and we shall try here to make the fraternity acquainted with the means used for purification of the carbonic acid gas in practical carbonating.

In the production of carbonic acid it occurs very often, especially when carelessly manipulating, that the sulphuric acid and marble is allowed to mix very rapidly in the generator, the cause of which will be, that a large volume of gas is suddenly evolved and will carry over with itself, in very fine particles, sulphuric acid and marble, assuming the form of gas, into the purifier, which the water cannot reach when the gas passes through the purifier in large bubbles. To prevent this and break and subdivide the gas bubbles the perforated diaphragm, already mentioned, is placed in the purifier. In this the gas cannot pass upwards in large bubbles, but it is cut into minute particles, whereby the whole gas comes in contact with the water or purifying material, and all impurities which it may have chanced to carry along with itself from the generating chamber of the apparatus are left in the water of the purifiers, and a purer carbonic acid gas is obtained.

For the same purpose, and also to remove or absorb the sulphuric (or muriatic) acid, chunks of marble are already recommended to be placed in purifiers, and we strongly recommend the diaphragm in addition, and hereafter we shall find some more remedies for it. It often occurs, also, that the chemical action of the sulphuric acid (see also muriatic acid) on the carbonate produces excessive hot generators, and therefore very naturally also hot carbonic acid of bad odor in consequence, which the water will assume if the gas is not previously purified before entering it. Even when all precautions in generating the carbonic acid gas are taken, the eliminating gas may be contaminated by bad odors of impurities in the acid or in the carbonate, as pointed out already, and consequently spoil the beverage.