Monthly Archives: June 2014

Potassium Hydroxide.

Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.

Potassium Hydroxide is noteworthy as the precursor to most soft and liquid soaps as well as numerous potassium-containing chemicals.

Potassium hydroxide can be found in pure form by reacting sodium hydroxide with impure potassium. Potassium hydroxide is usually sold as white or translucent pellets, sometimes yellow, which will become tacky in air because KOH is hygroscopic. Consequently, KOH typically contains varying amounts of water (as well as carbonates).


Its dissolution in water is strongly exothermic, meaning the process gives off significant heat. Concentrated aqueous solutions are sometimes called potassium lyes. Even at high temperatures, solid KOH does not dehydrate readily.

Potassium hydroxide has many uses:-

  • Precursor to other potassium compounds, eg fertilisers
  • Manufacture of biodiesel
  • Manufacture of soft soaps
  • As an electrolyte
  • Cleaning and disinfection
  • As a main active ingredient in chemical “cuticle removers” used in manicure treatments

Health information

  • Potassium Hydroxide is highly corrosive and contact can severely irritate and burn the skin and eyes leading to damage
  • Potassium Hydroxide can affect you when inhaled and by passing through the skin
  • Contact can irritate the nose and throat
  • Inhaling can irritate the lungs causing a build up of fluid
  • Exposure can cause headaches, dizziness, nausea and vomiting
  • It may cause skin allergy.


All health and safety data information must be followed when using this chemical

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Ultrasonic Baths

An ultrasonic cleaner is a cleaning device that uses ultrasound (usually from 20–400 kHz) and an appropriate cleaning solvent (sometimes ordinary tap water) to clean delicate items. The ultrasound can be used with just water, but use of a solvent appropriate for the item to be cleaned and the soiling enhances the effect. Cleaning normally lasts between three and six minutes, but can also exceed 20 minutes, depending on the object to be cleaned.


Ultrasonic cleaning penetrates even microscopic openings to provide complete cleaning of the objects treated. This makes it one of the most effective, economical and powerful cleaning methods available. It has applications in laboratories, dental and medical technology, microelectronics, precision engineering, cosmetics, optics and the automotive industry. Ultrasonic cleaners are used to clean many different types of objects, including jewellery, lenses and other optical parts, watches, dental and surgical instruments, tools, coins, fountain pens, golf clubs, window blinds, firearms, musical instruments, industrial parts and electronic equipment. They are used in many jewellery workshops, watchmakers’ establishments, and electronic repair workshops               

Modern baths tend to have a heavy duty ultrasonic generator which ensures that the ultrasonic output remains constant, regardless of the bath temperature, fill level and cleaning material. This feature guarantees consistent and reproducible cleaning results. ‘Frequency sweeping’, a frequency modulation of the ultrasonic output generated, prevents ‘standing waves’ from being generated and ensures extremely homogeneous energy distribution in the cleaning bath.
 
Ultrasonic cleaning uses Cavitation bubbles induced by high frequency pressure (sound) waves to agitate a liquid. The agitation produces high forces on contaminants adhering to substrates like metals, plastics, glass, rubber, and ceramics. This action also penetrates blind holes, cracks, and recesses. The intention is to thoroughly remove all traces of contamination tightly adhering or embedded onto solid surfaces. Water or other solvents can be used, depending on the type of contamination and the workpiece.
 
There are various ways to test the level of ultrasonic activity within an ultrasonic bath..
 
There are a number of recommended tests for establishing levels of ultrasonic activity in the bath.

The foil test involves suspending a strip of foil into various locations around the tank. The foil should not touch the base of the tank and should be held in position for around 1 minute. It should then be removed and there should be an even distribution of perforations and small holes on the surface of the foil.

Another test requires the use of Brownes soil test strips. These are plastic strips which have been contaminated to simulate the contamination which might affect surgical instruments. After running an ultrasonic cycle the strips should be taken from the bath and all contamination should have been removed.

An ultrasonic energy meter can also be used to test the level of ultrasonic activity within the tank.

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Pyroclastic flows

Pyroclastic flows are high-density mixtures of hot, dry rock fragments and hot gases that move away from the vent that erupted them at high speeds. They may result from the explosive eruption of molten or solid rock fragments, or both. They may also result from the nonexplosive eruption of lava when parts of dome or a thick lava flow collapses down a steep slope. Most pyroclastic flows consist of two parts: a basal flow of coarse fragments that moves along the ground, and a turbulent cloud of ash that rises above the basal flow. Ash may fall from this cloud over a wide area downwind from the pyroclastic flow.


Pyroclastic flows can reach speeds moving away from a volcano of up to 700 km/h (450 mph).  The gas can reach temperatures of about 1,000 °C (1,830 °F). Pyroclastic flows normally hug the ground and travel downhill, or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope. They are a common and devastating result of certain explosive volcanic eruptions.

A pyroclastic flow will destroy nearly everything in its path. With rock fragments ranging in size from ash to boulders traveling across the ground at speeds typically greater than 80 km per hour, pyroclastic flows knock down, shatter, bury or carry away nearly all objects and structures in their way. The extreme temperatures of rocks and gas inside pyroclastic flows can cause combustible material to burn, especially petroleum products, wood, vegetation, and houses.

Testimonial evidence from the 1883 eruption of Krakatoa, supported by experimental evidence, shows that pyroclastic flows can cross significant bodies of water. One flow reached the Sumatran coast as much as 48 km away.

Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984


The towns of Pompeii and Herculaneum, Italy, for example, were engulfed by pyroclastic surges in 79 AD with many lives lost.

“Garden of the Fugitives”. Plaster casts of victims still in situ; many casts are in the Archaeological Museum of Naples.

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Antimony

Antimony is a chemical element with symbol Sb (from Latin: stibium) and atomic number 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3).

 


Antimony compounds have been known since ancient times and were used for cosmetics.  Nowadays Antimony is mainly used as its trioxide in making flame-proofing compounds and in certain alloys.  The Egyptians had a hieroglyph for Antimony……


Antimony has no known biological role, but it is a potent toxin, with effects that are similar to arsenic poisoning. When ingested, antimony strongly bonds to sulfur-containing enzymes, thereby inactivating them. Antimony is even more toxic when inhaled as the gas, stibine, SbH3. Poisoning by antimony ingestion manifests as gastric distress, and large doses cause vomiting, and kidney and liver damage, followed by death a few days later.

It was thought that Mozart was a victim of poisoning at the hand of rival composer, Antonio Salieri, although historians don’t give this hypothesis any credence. It is far more likely that Mozart was poisoned by his doctors. A heavy drinker, Mozart was known to also overindulge in the popular hangover cure of the day that contains antimony, tartar emetic, C4H4KO7Sb, which was provided by his doctors.

Stibnite


For some time, China has been the largest producer of antimony and its compounds, with most production coming from the Xikuangshan Mine in Hunan. The industrial methods to produce antimony are roasting and subsequent carbothermal reduction or direct reduction of stibnite with iron.

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