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laboratory uses of HCl
                                                                                                       LABORATORY USE OF HCl
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When using Hydrochloric Acid in the laboratory, it is important that due consideration is given to the potential hazards of the material.  Safe and careful handling of the product is essential; this will include using Personal Protective Equipment (PPE) comprising protective clothing, safety shoes or boots, rubber gloves and approved eye protection.  Where large volumes of material are being used, breathing apparatus may be required.  Where splashes may occur, full face protection should always be used.  When using Hydrochloric Acid in the laboratory, adequate fume extraction should always be used as the fumes from Hydrochloric Acid can cause serious damage to nasal passages, soft tissue of the respiratory tract and the lungs themselves.  Ingestion of Hydrochloric Acid can result in burns to the mouth, oesophagus and digestive tract and even at low levels, ingestion can cause serious damage to the teeth.
When working with Hydrochloric Acid in the laboratory, it is essential to be aware of the fact that the product produces 'Hazardous' reactions with a range of materials.  For example, Hydrochloric Acid reacts with Sodium Hypochloride  and Potassium Permanganate to produce 'Toxic' Hydrogen Cyanide.  Hydrochloric Acid also reacts with most base metals to produce Hydrogen gas.  Hydrochloric Acid produces as 'exothermic' reaction with Sodium Hydroxide.  This means that heat is generated when the two materials come into contact.  Hydrochloric Acid also reacts with Ammonia, in this case producing dense white fumes of Ammonium Chloride.  It is essential that Hydrochloric Acid containers are stored appropriately.  If exposed to heat, the containers may be in danger of explosing.
Due to its covalent, polarised bond, Hydrochloric Acid is a highly useful laboratory reagent, not only as a titrant to standardise alkali solutions, but also as a catalyst in organic chemistry.
One of the most common uses of Hydrochloric Acid in the laboratory is with Nitric Acid in Aqua Regia.  This solution is one of the few solutions capable of dissolving both gold and platinum which, in turn, can be used to purify both metals.  As well as cleaning and etching glassware, Aqua Regia is also the preferred cleaning medium for NMR tubes as it does not leave any ionic residues , unlike the alternative Chromic Acid  which is susceptible to leaving residues.
On a more mundane level, Hydrochloric Acid is used to assay strong alkalies conforming to the basic equation:
Acid  +  Base  >  Salt  +  Water
These titrations can be carried out manually with the aid of an indicator or automatically with an autotitrator, where the end point is defined by the largest change in electrical current.
Similarly, Hydrochloric Acid can be used to standardise Silver Nitrate by argentometric titration:-
AgNO3  +  HCl  >  AgCl  +  HNO3
Again, this can be carried out manually or electrochemically, the latter possibly having the edge in this case as the indicators involved are notoriously subjective with their end points.
Another use of Hydrochloric Acid in the laboratory is to adjust the pH of buffer solutions for the calibration of pH meters as these regularly do not come out to their exact value.  Most buffers, once manufactured, can be trimmed to the required value by small adjusments with a weak solution of Hydrochloric Acid in water.
As mentioned previously, another use of Hydrochloric Acid in the laboratory, is as a catalyst for some organic reactions, although these are not widely carried out on a laboratory scale.  The most notable of these is the production of the non-stick coating Teflon, the refrigerant Freon, the elastomer Neoprene and Polyvinyl Chloride or PVC.
Hydrochloric Acid can be classified as 'Corrosive' or 'Irritant' depending on its strength.  For solutions above 25% by weight, the classification is 'Corrosive'; between 10% and 25% the classification is 'Irritant'.  Hydrochloric Acid can be produced in concentrated form between 36% and 40% when it is often referred to as 'fuming' Hydrochloric Acid.  The word 'fuming' relates to the fumes that appear when it is produced in its most concentrated form.  Although it is technically possible to produce Hydrochloric Acid in a concentration of 40%, this is unrealistic as evaporation would hamper its use.  Hydrochloric Acid is often used in dilute form of 10% to 15%, particularly when used for domestic applications.
Hydrochloric Acid has many uses in industry.  For example, it is used in the steel-making industry where its properties to remove rust from metals are known as 'pickling'.  It is used in food preparation, both for canning, for sauces and particulary in the manufacture of corn syrups for soft drinks.  Hydrochloric Acid is used in the building industry or concrete-etching and brick cleaning.  It is used in many household cleaning products in a diluted form.  Hydrochloric Acid is also used in swimming pool cleaning and maintenance products.
Hydrochloric Acid packaging, labelling and transport are governed by legislation and full details of these requirements can be found on the relevant web pages of this website.  Separate webpages also outline Hydrochloric Acid Hazards and Hydrochloric Acid safety requirements.  Hydrochloric Acid is also known as Muriatic Acid and its chemical name is HCl.  In its concentrated form, Hydrochloric Acid is known as Fuming Hydrochloric Acid, Fuming Muriatic Acid and Fuming HCl.


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