Tech Tips

Acetic Acid
Acetic Acid is a weak acid in terms of chemical ionization, and solutions of it can be assayed with a standardized solution of a strong base, such as Sodium Hydroxide.  Full story...

Ammonium Hydroxide
Ammonium Hydroxide is a weak base in terms of chemical ionization, and solutions of it can be assayed with a standardized solution of a strong acid, such as Hydrochloric Acid or Sulfuric Acid.  Full story...

Ammonium Thiocyanate
Ammonium Thiocyanate solution can be used in titrations involving Silver Nitrate solutions.  Full story...

Arsenic Trioxide
Arsenic Trioxide, As2O3, is a very good reductometric primary standard but it dissolves slowly in water.  Full story...

Ceric Sulfate
Ceric Sulfate is a powerful and versatile oxidizing agent that possesses certain advantages over Potassium Dichromate and Potassium Permanganate.  Full story...

Color Standards
Color can be one of the most obvious indications of contamination or deterioration.  Full story...

Conductivity Standards
Conductivity is a measure of the ability of an aqueous solution to carry an electric current. This ability depends on the presence of ions; on their total concentration, mobility and valence; and on the temperature of measurement.  Full story...

Copper Sulfate
The minimum requirement of the American Association of Blood Banks (AABB) and the Food and Drug Administration (FDA) for suitable blood donors is 12.5 g/dL hemoglobin level or 38% packed cell volume (hematocrit) for fingerstick or venipuncture sampling methods. Copper Sulfate Solution, Specific Gravity 1.053, Group No. 2330, is equivalent to these limits.  Full story...

Density and Specific Gravity
Density and Specific Gravity are related concepts that are often confused. Density is defined as the ratio of the mass (weight) to volume of a substance.  Full story...

EDTA (Disodium)
EDTA is the commonly used abbreviation for (Ethylene­dinitrilo)­tetra­acetic Acid (also called Ethylene­diamine­tetra­acetic Acid or Edetic Acid).  Full story...

Ferrous Ammonium Sulfate
Ferrous Ammonium Sulfate solutions are used as reductometric standards in titrations involving Ceric, Dichromate and Permanganate ions, as well as other oxidizers.  Full story...

Hydrochloric Acid
Hydrochloric Acid is a strong acid in terms of chemical ionization, and solutions of it can be assayed with a standardized solution of a strong base, such as Sodium Hydroxide. The endpoint can be determined potentiometrically or by using a pH indicator.  Full story...

Iodine
Iodine, a diatomic molecule (I2), is an oxidizing agent and solutions of it are frequently used in chemical analyses. Iodine suffers from low solubility in water and its volatility makes it difficult to handle directly.  Full story...

Kjeldahl Analysis
The Kjeldahl method is an analytical method for the determination of Nitrogen in the trinegative state in certain organic compounds. The method was developed in 1883 by Johan Kjeldahl, a Danish chemist, and is used extensively in the determination of protein in foods, since protein is a macromolecule made up of Nitrogen-containing amino acids linked together.  Full story...

Mercuric Nitrate
Mercuric Nitrate reacts with Chloride ions to form soluble, mostly undissociated Mercuric Chloride, and is commonly used in the determination of Chloride. Diphenylcarbazone (DPC) is used as the indicator:  Full story...

Nitric Acid
Nitric Acid is a strong acid in terms of chemical ionization and solutions of it can be assayed using a strong base, such as Sodium Hydroxide. The endpoint can be determined potentiometrically or by using a pH indicator.  Full story...

Nitrogen Standards
Nitrogen standards can be confusing, because Nitrogen exists in so many forms and nomenclature is not always consistent. Our practice is to name each standard according to the species being measured.  Full story...

Oxidation-Reduction Potential
Oxidation-Reduction Potential (ORP) is measured using an inert (usually Platinum) electrode and a suitable reference electrode. The measured ORP depends on the choice of reference electrode.  Full story...

Perchloric Acid
Perchloric Acid is one of the strongest acids known. Solutions of Perchloric Acid in Glacial Acetic Acid are typically used in nonaqueous titrations of amines and other organic bases, as well as salts of organic acids (which act as bases in Glacial Acetic Acid).  Full story...

pH
The pH of a sample is an indication of its acidity or alkalinity and pH determination is one of the most commonly conducted laboratory measurements. The term pH is defined as the negative logarithm (base 10) of the Hydrogen ion concentration (or, more accurately, Activity) expressed in molarity.  Full story...

Phenylarsine Oxide
Phenylarsine Oxide (PAO) solutions are used as alternatives to Sodium Thiosulfate solutions and occasionally as a replacement for Sodium Arsenite in some analyses for Chlorine.  Full story...

Potassium Biiodate
Potassium Biiodate is a primary standard substance that can be used as a basimetric as well as an oxidimetric standard. In addition to its versatility, it has the advantage of a high equivalent weight, especially when used to standardize bases.  Full story...

Potassium Bromate
Potassium Bromate is a powerful oxidizing agent in acid solution and is a convenient, stable source for Bromine.  Full story...

Potassium Chromate
Potassium Chromate is used as an indicator in the determination of Chloride by titration with standard Silver Nitrate solution. This method is called the Mohr method of determining Chloride...  Full story...

Potassium Dichromate
Potassium Dichromate is a versatile, powerful oxidizing agent (although not as powerful as Potassium Permanganate) that also meets the requirements of being a primary standard.  Full story...

Potassium Hydrogen Phthalate
Potassium Hydrogen Phthalate (KHP) is a classic primary standard substance in that it is readily available in high purity; is relatively inexpensive; is easy to dry; is neither hygroscopic, oxidized by air, nor affected by Carbon Dioxide (thus making it easy to weigh out)...  Full story...

Potassium Hydroxide
Potassium Hydroxide is a strong base in terms of chemical ionization and solutions of it can be assayed using a strong acid, such as Hydrochloric Acid or Sulfuric Acid, or by using an acidimetric standard such as Potassium Hydrogen Phthalate (KHP).  Full story...

Potassium Iodate
Potassium Iodate is an oxidizing agent and a good primary standard with the one drawback of having a relatively low equivalent weight. It is used primarily as a stable source of Iodine, which is liberated in the presence of Iodide ion and acid, in the titration of Thiosulfate and Sulfite solutions.  Full story...

Potassium Permanganate
Potassium Permanganate is a versatile and powerful oxidant that can be used to determine many substances by direct or indirect titration. A unique advantage of Potassium Permanganate is that it serves as its own indicator.  Full story...

Potassium Thiocyanate
Potassium Thiocyanate solution can be used in titrations involving Silver Nitrate solutions. Chloride, Bromide and Iodide can be determined indirectly this way by adding excess Silver Nitrate solution to the sample containing the Halide, thus precipitating the Halide, and titrating the excess Silver Nitrate with Potassium Thiocyanate titrant using a Ferric Alum Indicator.  Full story...

Potassium Thiocyanate
Potassium Thiocyanate solution can be used in titrations involving Silver Nitrate solutions. Chloride, Bromide and Iodide can be determined indirectly this way by adding excess Silver Nitrate solution to the sample containing the Halide...  Full story...

Precision and Accuracy
Precision and accuracy are important concepts in chemical analysis. Precision refers to the exactness (related to repeatability) of a measurement, while accuracy refers to how close the measurement is to the “true” value.  Full story...

Silver Nitrate
Silver Nitrate solutions are used almost exclusively for the determination of Halides, i.e., Chloride, Bromide and Iodide. Silver Nitrate solutions can be standardized potentiometrically, or by using the Mohr method or the Volhard method.  Full story...

Sodium Carbonate
Sodium Carbonate is used as a basimetric standard but it is not a very good primary standard since it is difficult to dry, is hygroscopic, and has a relatively low equivalent weight. For these reasons, Tris(hydroxymethyl)aminomethane has largely replaced it as a basimetric standard.  Full story...

Sodium Hydroxide
Sodium Hydroxide is a strong base in terms of chemical ionization and solutions of it can be assayed using a strong acid, such as Hydrochloric Acid or Sulfuric Acid, or by using an acidimetric standard such as Potassium Hydrogen Phthalate (KHP).  Full story...

Sodium Thiosulfate
Sodium Thiosulfate solutions are almost exclusively used to standardize Iodine solutions or as back-titrants in titrations using Iodine. Solutions of Sodium Thiosulfate are most commonly standardized with Potassium Dichromate or Potassium Iodate solutions, which generate Iodine from Iodide.  Full story...

Starch
Starch solutions are used as indicators in the detection of the endpoint of titrations involving Iodine solutions. Starch reacts with Iodine in the presence of Iodide ion to form an intensely colored blue complex, which is visible at very low concentrations of Iodine, making it a very good indicator in both direct and indirect lodometric titrations.  Full story...

Sulfosalicylic Acid
Sulfosalicylic Acid solutions can be assayed with standardized Sodium Hydroxide solutions using Phenolphthalein Indicator according to the following reaction...  Full story...

Sulfuric Acid
Sulfuric Acid is a strong acid in terms of chemical ionization and solutions of it can be assayed using a strong base, such as Sodium Hydroxide or Potassium Hydroxide. The endpoint can be determined potentiometrically or by using a pH indicator.  Full story...

Trichloroacetic Acid
Trichloroacetic Acid (TCA) is a much stronger acid than Acetic Acid, from a chemical ionization standpoint, because the electronegative Chlorine atoms draw electron density away from the carboxyl end of the molecule, creating a partial positive charge on the carboxyl group, and allowing easier removal of the positively charged Hydrogen ion, H+.  Full story...

Turbidity
Turbidity is a measure of the cloudiness or haziness of a liquid.
It is related to the amount of light scattered or absorbed (as opposed to being transmitted) by the sample.  Full story...

Volumetric Glassware
Properly calibrated and performing volumetric glassware (e.g., pipets, burets and volumetric flasks) is essential to obtaining accurate analytical data and results. Even Class A volumetric glassware is not absolute but rather has a tolerance from its stated nominal value.  Full story...