Barium sulfate standard, preparation

Primer Formulations. Coatings were formulated using standard techniques. Mill bases were prepared by dispersing the oligomer solution with pigments (silica, carbon black, titanium dioxide and barium sulfate in a 1 1 1 10 ratio). The viscosity of the formulation was reduced to spray viscosity by addition of solvent. 

The addition of various modifiers, such as quinoline-sulfitr, thiourea, 52 or, especially, tetramethylthiourea 53 to the reaction mixture, is sometimes necessary in order to inhibit the further hydrogenation of the aldehyde. This is particularly true for the formation of aryl aldehydes that are hydrogenated over palladium under mild conditions. 54.155 barium sulfate support is, itself, a moderate inhibitor and is generally sufficient for regulating the preparation of unsubstituted aliphatic aldehydes. However, if another support, such as charcoal, is used for the palladium, one of the standard inhibitors must be added to moderate the reaction. When these added inhibitors are present, the... 

Step one in the test is to prepare a crystal seed by adding 1 ml of a 250 g/1 solution of barium chloride R to 1.5 ml of sulfate standard solution (10 ppm SO4) Rl. Shake and allow to stand for 1 min. Then, 15 ml of the solution to be examined and 0.5 ml of acetic acid R are combined. Prepare a standard in the same manner using 15 ml of sulfate standard solution (10 ppm SO4) Rl instead of the solution to be examined. After 5 min, any opalescence in the test solution should not be more intense than that in the standard. 

A 1 MacFarland standard is a suspension of a fine white precipitate of barium sulfate, which, when shaken up, approximates the turbidity of a bacterial suspension containing 3.0 x 10 organisms/mL. A 1 MacFarland standard is prepared by adding 0.1 mL of a 1% solution of barium chloride to 9.9 mL of 1% sulfuric acid. 

Hydrogenation of alkynes with this new catalyst gives the Z-alkene as the major product, with only trace amounts of the )-alkene. This selective catalyst is called the Lindlar catalyst and hydrogenation of alkynes using it is called Lindlar hydrogenation or Lindlar reduction, named for its discoverer, H. Lindlar (Switzerland). This catalyst has been supplanted by another version that is easier to prepare and less prone to the oxidation of the lead carbonate and lead oxide constituents. It is now the standard and is formally called the Rosenmund catalyst, but it is commonly referred to as a Lindlar catalyst. The new catalyst is composed of palladium-on-barium sulfate (BaS04) and it... 

---