Solar distillation can be used to make saline or brackish water potable. The first recorded instance of this was by 16th-century Arab alchemists. A large-scale solar distillation project was first constructed in 1872 in the Chilean mining town of Las Salinas. The plant, which had solar collection area of 4,700 m2 (51,000 sq ft), could produce up to 22,700 L (5,000 imp gal; 6,000 US gal) per day and operate for 40 years. Individual still designs include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick, and multiple effect. These stills can operate in passive, active, or hybrid modes. Double-slope stills are the most economical for decentralized domestic purposes, while active multiple effect units are more suitable for large-scale applications.
What is used to make saline or brackish water drinkable?
Solar distillation

In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted, such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution, correctly applied during preparation, may do much to reduce this problem but it is difficult to control completely, especially when using mass-produced kiln-dried timber stocks.
In what stage of processing does knot primer need to be applied for maximum effectiveness?
preparation

The description or representation of individual and group identity is a central task for psychologists, sociologists and anthropologists and those of other disciplines where "identity" needs to be mapped and defined. How should one describe the identity of another, in ways which encompass both their idiosyncratic qualities and their group memberships or identifications, both of which can shift according to circumstance? Following on from the work of Kelly, Erikson, Tajfel and others Weinreich's Identity Structure Analysis (ISA), is "a structural representation of the individual's existential experience, in which the relationships between self and other agents are organised in relatively stable structures over time … with the emphasis on the socio-cultural milieu in which self relates to other agents and institutions" (Weinreich and Saunderson, (eds) 2003, p1). Using constructs drawn from the salient discourses of the individual, the group and cultural norms, the practical operationalisation of ISA provides a methodology that maps how these are used by the individual, applied across time and milieus by the "situated self" to appraise self and other agents and institutions (for example, resulting in the individual's evaluation of self and significant others and institutions).[citation needed]
The central task for psychologists, sociologists, and anthropologists is to describe what topics?
individual and group identity