A glass of sparkling water please!

Carbonated water is known by many names- soda water, club soda, seltzer water, fizzy water, and sparkling water. It forms the backbone of all the carbonated beverages, several cocktails, and is becoming increasingly popular in cooking where it is used to provide a lighter texture to doughs and batters. The uses of club soda also extend beyond gluttony; it is used as a stain remover despite there being no scientific basis for why it would be superior to ordinary water. So what is carbonated water and how was it discovered?

Naturally carbonated waters are a common occurrence in springs when carbon dioxide (CO₂) bubbles through the water (H₂O). Artificially carbonated water, however, involves dissolving low concentrations of carbon dioxide in water. The reaction generates carbonic acid (H₂CO₃), which gives a slightly tart flavor to the carbonated water:

                                                   H₂O + CO₂ ⇌ H₂CO₃     

    

The above reaction is reversible- carbonic acid can easily dissociate to release carbon dioxide and water. Henry's Law states that the amount of a gas that can be dissolved in water depends on the temperature of the water and the pressure of the gas. Cold water will permit the maximum amount of carbon dioxide to dissolve in it. If the temperature of the water is increased or if the pressure of the gas is decreased, which happens when the container of carbonated water is opened, the carbon dioxide escapes in the form of bubbles. 

Figure 1: Bubbles of carbon dioxide in sparkling water. Source.

Artificially carbonated water was first made in 1750, by a French chemist Gabriel François Venel. He had observed the effervescent water of the Selz river in Germany. He attributed the effervescence to the escape of common air, which he called "superabundant air". In an attempt to replicate this phenomenon, he combined hydrochloric acid (HCl) and soda (NaHCO₃) to produce carbonated water resulting the following reaction:

                                                HCl + NaHCO₃  →  NaCl + H₂O + CO₂     

        

The other byproduct of the reaction is sodium chloride (NaCl) that we know as table salt.

It was only in 1754 that a Scottish chemist Joseph Black characterized the air bubbles as carbon dioxide. He passed the gas through lime (Ca(OH)₂), which produced a precipitate of calcium carbonate (CaCO₃):

                                               CO₂ + Ca(OH)₂   →  CaCO₃ + H₂O 

Figure 2: Test for carbon dioxide. From left to right: test tube containing calcium hydroxide, bubbling carbon dioxide through the calcium hydroxide solution, formation of calcium carbonate. Source.

In 1767, an English chemist Joseph Priestly discovered how to produce drinkable carbonated water. He utilized the fact that carbon dioxide is released as a byproduct during the production of beer; he  suspended a bowl of water over a beer vat at a local brewery, which impregnated the water with carbon dioxide. Priestly realized that the resulting water had a pleasant taste and could be offered as a refreshing drink. In 1772 he developed an apparatus to do the same. He used sulfuric acid (H₂SO₄) and chalk (CaCO₃) to generate carbon dioxide which was then dissolved in an agitated bowl of water:

                                             H₂SO₄ + CaCO₃   →   CaSO₄ + H₂O + CO₂     

Figure 3: Directions for producing carbonated water in Joseph Priestly's book Impregnating Water with Fixed Air. The procedure involved using a glass vessel (labelled "a" in Figure 1) that was inverted into a bowl of water "b". Pipe "c" connected the bowl to a bladder "d" which was fit into a phial "e". Initially the phial was filled with chalk and water. Sulfuric acid was then added to this mixture in small amounts. Once the effervescence started, the phial was stoppered, and the carbon dioxide released passed through the pipe and into the water in the inverted glass vessel. Source. 

J. J. Schweppe, a Swiss watchmaker, improved on Priestley's method and developed the first practical method to manufacture carbonated water on a large scale. This led to the founding of the Schweppes company in 1783. He also tried to move the business to London but was unsuccessful. However, the drink was later popularized by Erasmus Darwin, the grandfather of Charles Darwin, and by King William IV of the United Kingdom who adopted the beverage with the Royal Warrant of Appointment.

Packaging woes

The bottles containing carbonated beverages were usually sealed with a cork. The main disadvantage of using a cork was that the bottles could not be stored upright- the corks had a tendency to dry out and shrink thereby allowing the gas to be released and causing the bottle to "pop". Therefore these bottles were stored on their side, which prevented the corks from drying out. Furthermore, it was difficult to open the bottles by hand; a fact that was wonderfully depicted by the British painter William H.H. Trood.

Figure 4: The paintings "Uncorking Bottle" and "Surprising Result". Source.

To circumvent the problem of using corks, in 1872 a British soft drink maker Hiram Codd designed the Codd-neck bottle to store carbonated drinks. The neck of the bottle enclosed a marble and a rubber gasket. These bottles were then filled upside down with the carbonated beverage and the pressure of the gas forced the marble up, thereby sealing in the carbonation. The bottle also contained a chamber into which the marble was pushed to open the bottle. This prevented the marble from blocking the neck of the bottle as the drink was poured. However, the design had an unsanitary disadvantage that lead to a decline in it's popularity- people would generally use their fingers to push down the marble.

Figure 5: The Codd-neck bottle. Source.

Another improvement in bottle design took place in 1874 when an American inventor Charles de Quillfeldt invented the flip-top bottle. The mouth of the bottle was sealed by a stopper, fitted with a rubber gasket, and held in place by a set of wires. This allowed the bottle to be opened and resealed repeatedly without the use of a bottle opener. 

Figure 6: The top of a flip-top bottle. Source. 

The pièce de résistance in the manufacturing of bottle caps was the invention of the crown cork in 1892 by the American engineer William Painter. He also invented bottle openers to enable the removal of these metal bottle caps. The crown cork bottle stopper allowed the soda bottles to be stored standing upright.

Figure 7: The "Bottle Sealing Device" patents issued in 1892. Source. 

What's in a name?                    

If you want to order carbonated water at a restaurant, what should you ask for? As previously mentioned, there are several types of carbonated water. Soda water, sparkling water, and fizzy water are used to describe any type of carbonated water. However, club soda and seltzer water do have a few defining characteristics. Club soda refers to artificially carbonated water to which sodium salts and/or potassium salts have been added. In contrast, seltzer water is artificially carbonated water which does not contain any added ingredients. Seltzer water gets it name from the town of Selters in Germany, which was renowned for its natural springs. Cheers!