History of dry cleaning

The exact date of discovery of dry cleaning is not known. An anecdote tells us that in about 1820 in Paris, a lamp filled with turpentine fell down by accident and wetted a textile. After the turpentine was vaporized, the wetted areas of the textile were clean, because the turpentine dissolved oily and greasy stains from it. 

In 1825, Jolly Belin founded the first commercial dry laundry in Paris. He soaked textile apparel in a wooden tub filled with turpentine, cleaned them by manual mechanical action, and dried them by evaporating the turpentine in the air. 

After getting the know-how to distill benzene from tar of hard coal in 1849, this was used as a solvent for dry cleaning because of its far better cleaning power. But benzene is a strong poison, so it was changed some decades later to petrol, which is explosive. In order to reduce this risk, petrol as dry cleaning solvent was changed to white spirit (USA Stoddard solvent) with a flash point of 40 - 60°C (100 - 140°F) in 1925. 

Compared to TCE, fluorinated chlorinated hydrocarbons (CFC) offer benefits to dry cleaning because of their lower boiling points and their more gentle action to dyestuffs and fabrics. So since 1960 these solvents have had some importance in North America, Westem Europe, and the F ar East. They were banned because of their influence on the ozone layer in the stratosphere by the UNESCO s Montreal Protocol in 1985. 

At the same time, TCE was classified as a contaminant to groundwater and as a dangerous chemical to human health with the possible potential of cancerogenic properties. As a result of this, hydrocarbon solvents on the basis of isoparaffins with a flash point higher 

alternatives to conventional dry cleaning were developed. Wet cleaning was introduced by Kreussler in 1991 (Miele System Kreussler) and textile cleaning in liquid carbon dioxide was exhibited by Global Technologies at the Clean Show Las Vegas in 1997. 

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World capacity and demand for tetrachloroethylene were approximately 1100 and 845 thousand metric tons ia 1974, respectively. Although demand iacreased iato the mid-1980s, siace then demand for tetrachloroethylene has decreased significantly as a result of the phaseout of chlorofluorocarbons, the use of more efficient dry-cleaning equipment, and iacreased reclamation of waste solvent. World capacity and demand as of 1988 are provided ia Table 2 Several United States manufacturers have shut down faciUties ia the last fifteen years. Current manufacturers and their capacities are Hsted ia Table 3. United States production and sales history is shown ia Table 4. 

The quality of the tube (e.g., concentricity, wall thickness) is very important when very good resolution is required. Also, each type of probe has a lowest recommended quality sample tube and the use of lower quality tubes can lead to the damage of the probe. Each manufacturer specifies the quality parameters in terms of inner and outer diameters, waU thickness and concentricity. Each product has a specified tolerance for these parameters. Apart form the catalogue quality, the history of the tube is also very important (e.g., how it was cleaned, dried, stored, even what samples have been previously analyzed in it, as these operations might lower its quahty). 

Stable samples deposited on plates can be stored for relatively long periods of time. Although it is recommended not to reuse plates, well-cleaned plates are reusable. In any case, it is essential to keep the plates clean, dry, unscratched, and uncorroded. Maintaining records of the history of sample spots is highly recommended. Most plate manufacturers provide forms that can be used for record keeping. 

One of the major risk factors is a history of AD. The possibility of hand eczema occurring later in life increases significantly if the AD was severe during childhood and was localised in the hands (60-90% of these patients and 40% of patients with moderate AD develop hand eczema later in working life). The risk of hand dermatitis decreases if the AD was mild. The risk of developing hand dermatitis has been estimated to be threefold in atopic relative to non-atopic workers if there is exposure to skin-irritating factors. Episodes of hand eczema can occur in patients predisposed to AD, even if they are not in working life or are just in clean, dry office work. 

Before silylation, the ceramic substrate must be cleaned and hydroxylated. Silica substrates can be treated with a dilute acid solution to remove traces of iron ions and organic solvents. The substrate is then rinsed with deionized water for a prescribed period to hydrolyze, if necessary, any surface siloxane groups into silanol groups. The final pretreatment step involves drying in order to remove exeess surface water. Alflioughflie average surface density on a hydroxylated amorphous siliea is 4.6 hydroxyls/nm [53], the actual surface distribution of silanol and siloxane groups depends on the temperature history of the substrate and the type of solvent employed in die hydrolysis [54]. 

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