Instruct: Given a question, retrieve relevant passages that answer the question.
Query: What is an alkali?
In chemistry, an alkali (/ˈælkəlaɪ/; from Arabic: al-qaly "ashes of the saltwort") is a basic, ionic salt of an alkali metal or alkaline earth metal chemical element. An alkali also can be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The adjective alkaline is commonly, and alkalescent less often, used in English as a synonym for basic, especially for bases soluble in water. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base, and they are still among the most common bases.
Lithium, the lightest of the alkali metals, is the only alkali metal which reacts with nitrogen at standard conditions, and its nitride is the only stable alkali metal nitride. Nitrogen is an unreactive gas because breaking the strong triple bond in the dinitrogen molecule (N) requires a lot of energy. The formation of an alkali metal nitride would consume the ionisation energy of the alkali metal (forming M ions), the energy required to break the triple bond in N and the formation of N ions, and all the energy released from the formation of an alkali metal nitride is from the lattice energy of the alkali metal nitride. The lattice energy is maximised with small, highly charged ions; the alkali metals do not form highly charged ions, only forming ions with a charge of +1, so only lithium, the smallest alkali metal, can release enough lattice energy to make the reaction with nitrogen exothermic, forming lithium nitride. The reactions of the other alkali metals with nitrogen would not release enough lattice energy and would thus be endothermic, so they do not form nitrides at standard conditions. Sodium nitride (NaN) and potassium nitride (KN), while existing, are extremely unstable, being prone to decomposing back into their constituent elements, and cannot be produced by reacting the elements with each other at standard conditions. Steric hindrance forbids the existence of rubidium or caesium nitride. However, sodium and potassium form colourless azide salts involving the linear anion; due to the large size of the alkali metal cations, they are thermally stable enough to be able to melt before decomposing.
Many other substances are similar to the alkali metals in their tendency to form monopositive cations. Analogously to the pseudohalogens, they have sometimes been called "pseudo-alkali metals". These substances include some elements and many more polyatomic ions; the polyatomic ions are especially similar to the alkali metals in their large size and weak polarising power.
The alkali feldspar group are those feldspar minerals rich in the alkali elements like potassium and sodium. The alkali feldspars include albite, anorthoclase, microcline, orthoclase and sanidine. Albite is considered as one of the alkali feldspars according to its chemical composition and it is also the alkali endmember of the plagioclase series.
A problem throughout the valley occurred as farmers irrigated land, which dropped the water table and caused alkali in the soil to rise. The alkaline soil eroded adobe structures and caused many crops to fail. As the alkali in the soil concentrated, the residents of Desert Lake moved about away and founded the town of Victor. A few log homes make up what's left of the town of Desert Lake.
Indeed, geopolymer cement is sometimes mistaken for alkali-activated cement and concrete, developed more than 50 years ago by V.D. Glukhovsky in Ukraine, the former Soviet Union. They were originally known under the names "soil silicate concretes" and "soil cements". Because Portland cement concretes can be affected by the deleterious "Alkali-aggregate reaction", coined AAR or Alkali-silica reaction coined ASR (see for example the RILEM Committee 219-ACS Aggregate Reaction in Concrete Structures ), the wording "alkali-activation" has a negative impact on civil engineers. However, geopolymer cements do not in general show these deleterious reactions (see below in Properties), when an appropriate aggregate is selected. In addition, "alkali-activated materials" are not polymers, so they cannot be called and mistaken for geopolymers. Indeed, the polymer chemistry is radically different compared to the calcium hydrate or precipitate chemistry. Nevertheless, several cement scientists continue to promote the terminology related to "alkali-activated materials" or "alkali-activated geopolymers". These cements, abbreviated AAM, encompass the specific fields of alkali-activated slags, alkali-activated coal fly ashes, and various blended cementing systems (see RILEM Technical committee 247-DTA).
The alkali metals are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation by atmospheric moisture and oxygen (and in the case of lithium, nitrogen). Because of their high reactivity, they must be stored under oil to prevent reaction with air, and are found naturally only in salts and never as the free elements. Caesium, the fifth alkali metal, is the most reactive of all the metals. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, excluding hydrogen (H), which is nominally a group 1 element but not normally considered to be an alkali metal as it rarely exhibits behaviour comparable to that of the alkali metals. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones.
An acid–alkali reaction is a special case of an acid–base reaction, where the base used is also an alkali. When an acid reacts with an alkali salt (a metal hydroxide), the product is a metal salt and water. Acid–alkali reactions are also neutralization reactions.
The difference between a basic salt and an alkali is that an alkali is the soluble hydroxide compound of an alkali metal or an alkaline earth metal. A basic salt is any salt that hydrolyzes to form a basic solution. 
A typical school demonstration demonstrates what happens when a piece of an alkali metal is introduced to a bowl of water. A vigorous reaction occurs, producing hydrogen gas and the specific alkali hydroxide. For example, if sodium is the alkali metal:
The 1863 Act was extended and expanded at least three times: first by the Alkali, &c. Works Regulation Act 1881, thence by the Alkali, &c. Works Regulation Act 1892, and subsequently by the Alkali, &c. Works Regulation Act 1906.
Before the industrial revolution alkali was mostly used to aid the bleaching process of cloth. As the industrial revolution took hold, increasing demand for alkali came from higher production of dyestuffs, and bleach. In 1798 John Losh and the Earl of Dundonald took out a lease for a rich supply of brine pumped from a nearby coal mine, the Walker pit, becoming the supplier of raw material for The Losh, Wilson & Bell Alkali works. The works were established at Walker-on-Tyne in 1807 and bleaching powder manufacture began there in 1830, Losh Brothers soon manufactured half the soda in England. By 1814 the Leblanc process of making alkali from common salt was introduced to Britain. Alkali works using this process opened at Tyne Dock 1822, Felling shore Tyneside 1826, Friars Goose Gateshead 1828 and again on Felling Shore in 1834. Such works also produced soda, alum and Epsom salts. 
The river frontage at South Shore of the River Tyne at Gateshead was one of the main locations for the chemical industry such that in the 19th century, which led to a cluster of iron, soap and alkali manufacturing. By 1828 the alkali works had large problem controlling emissions of hydrochloric acid fumes which devastated the neighbouring countryside. One solution was to build tall chimneys to drive the fumes further away and in 1833 the tallest chimney in England was built at the Friars Goose Alkali Works. The passing of the Alkali Act of 1863 in the UK Parliament brought about a further reduced pollution from these processes and was the first industrial environmental legislation to come into practice globally.
Rather than being neutral (as some other salts), alkali salts are bases as their name suggests. What makes these compounds basic is that the conjugate base from the weak acid hydrolyzes to form a basic solution. In sodium carbonate, for example, the carbonate from the carbonic acid hydrolyzes to form a basic solution. The chloride from the hydrochloric acid in sodium chloride does not hydrolyze, though, so sodium chloride is not basic.
The Forty Mile Desert was a barren stretch of waterless alkali wasteland that stretched from Humboldt Bar to both the Carson and Truckee rivers and beyond. The desert covered an area of over by , forming a fire box: its loose, white, salt-covered sands and baked alkali clay wastes reflected the sun's heat onto the stumbling travelers and animals. What few plants there are typically covered with thorns and live low to the ground.
Although francium is the heaviest alkali metal that has been discovered, there has been some theoretical work predicting the physical and chemical characteristics of the hypothetical heavier alkali metals. Being the first period 8 element, the undiscovered element ununennium (element 119) is predicted to be the next alkali metal after francium and behave much like their lighter congeners; however, it is also predicted to differ from the lighter alkali metals in some properties. Its chemistry is predicted to be closer to that of potassium or rubidium instead of caesium or francium. This is unusual as periodic trends, ignoring relativistic effects would predict ununennium to be even more reactive than caesium and francium. This lowered reactivity is due to the relativistic stabilisation of ununennium's valence electron, increasing ununennium's first ionisation energy and decreasing the metallic and ionic radii; this effect is already seen for francium. This assumes that ununennium will behave chemically as an alkali metal, which, although likely, may not be true due to relativistic effects. The relativistic stabilisation of the 8s orbital also increases ununennium's electron affinity far beyond that of caesium and francium; indeed, ununennium is expected to have an electron affinity higher than all the alkali metals lighter than it. Relativistic effects also cause a very large drop in the polarisability of ununennium. On the other hand, ununennium is predicted to continue the trend of melting points decreasing going down the group, being expected to have a melting point between 0 °C and 30 °C.
The stabilisation of ununennium's valence electron and thus the contraction of the 8s orbital cause its atomic radius to be lowered to 240 pm, very close to that of rubidium (247 pm), so that the chemistry of ununennium in the +1 oxidation state should be more similar to the chemistry of rubidium than to that of francium. On the other hand, the ionic radius of the Uue ion is predicted to be larger than that of Rb, because the 7p orbitals are destabilised and are thus larger than the p-orbitals of the lower shells. Ununennium may also show the +3 oxidation state, which is not seen in any other alkali metal, in addition to the +1 oxidation state that is characteristic of the other alkali metals and is also the main oxidation state of all the known alkali metals: this is because of the destabilisation and expansion of the 7p spinor, causing its outermost electrons to have a lower ionisation energy than what would otherwise be expected. Indeed, many ununennium compounds are expected to have a large covalent character, due to the involvement of the 7p electrons in the bonding.
Not as much work has been done predicting the properties of the alkali metals beyond ununennium. Although a simple extrapolation of the periodic table would put element 169, unhexennium, under ununennium, Dirac-Fock calculations predict that the next alkali metal after ununennium may actually be element 165, unhexpentium, which is predicted to have the electron configuration [Og] 5g 6f 7d 8s 8p 9s. Furthermore, this element would be intermediate in properties between an alkali metal and a group 11 element, and while its physical and atomic properties would be closer to the former, its chemistry may be closer to that of the latter. Further calculations show that unhexpentium would follow the trend of increasing ionisation energy beyond caesium, having an ionisation energy comparable to that of sodium, and that it should also continue the trend of decreasing atomic radii beyond caesium, having an atomic radius comparable to that of potassium. However, the 7d electrons of unhexpentium may also be able to participate in chemical reactions along with the 9s electron, possibly allowing oxidation states beyond +1, whence the likely transition metal behaviour of unhexpentium. Due to the alkali and alkaline earth metals both being s-block elements, these predictions for the trends and properties of ununennium and unhexpentium also mostly hold quite similarly for the corresponding alkaline earth metals unbinilium (Ubn) and unhexhexium (Uhh).
The alkali hydroxides are a class of chemical compounds which are composed of an alkali metal cation and the hydroxide anion (OH). The alkali hydroxides are:
As shown in the QAPF diagram, alkali feldspar granite contains between 20% - 60% quartz. Less quartz content would lead to "quartz alkali feldspar syenite". More than 90% of the total feldspar content is in the form of alkali feldspar. Less than that amount would designate the rock as a granite.
The alkali metals all have the same crystal structure (body-centred cubic) and thus the only relevant factors are the number of atoms that can fit into a certain volume and the mass of one of the atoms, since density is defined as mass per unit volume. The first factor depends on the volume of the atom and thus the atomic radius, which increases going down the group; thus, the volume of an alkali metal atom increases going down the group. The mass of an alkali metal atom also increases going down the group. Thus, the trend for the densities of the alkali metals depends on their atomic weights and atomic radii; if figures for these two factors are known, the ratios between the densities of the alkali metals can then be calculated. The resultant trend is that the densities of the alkali metals increase down the table, with an exception at potassium. Due to having the lowest atomic weight and the largest atomic radius of all the elements in their periods, the alkali metals are the least dense metals in the periodic table. Lithium, sodium, and potassium are the only three metals in the periodic table that are less dense than water: in fact, lithium is the least dense known solid at room temperature.
Alkali manufacture is the process by which an alkali is made. Typical alkalis, produced commercially, include sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate.
The production of pure alkali metals is somewhat complicated due to their extreme reactivity with commonly used substances, such as water. From their silicate ores, all the stable alkali metals may be obtained the same way: sulfuric acid is first used to dissolve the desired alkali metal ion and aluminium(III) ions from the ore (leaching), whereupon basic precipitation removes aluminium ions from the mixture by precipitating it as the hydroxide. The remaining insoluble alkali metal carbonate is then precipitated selectively; the salt is then dissolved in hydrochloric acid to produce the chloride. The result is then left to evaporate and the alkali metal can then be isolated. Lithium and sodium are typically isolated through electrolysis from their liquid chlorides, with calcium chloride typically added to lower the melting point of the mixture. The heavier alkali metals, however, is more typically isolated in a different way, where a reducing agent (typically sodium for potassium and magnesium or calcium for the heaviest alkali metals) is used to reduce the alkali metal chloride. The liquid or gaseous product (the alkali metal) then undergoes fractional distillation for purification. Most routes to the pure alkali metals require the use of electrolysis due to their high reactivity; one of the few which does not is the pyrolysis of the corresponding alkali metal azide, which yields the metal for sodium, potassium, rubidium, and caesium and the nitride for lithium.
Alkali basalt or alkali olivine basalt is a fine-grained, dark-coloured, volcanic rock characterized by phenocrysts of olivine, titanium-rich augite, plagioclase feldspar and iron oxides. For similar SiO concentrations, alkali basalts have a higher content of the alkalis, NaO and KO, than other basalt types such as tholeiites. They are also characterized by the development of modal nepheline in their groundmass (visible at highest magnification on a petrographic microscope) and normative nepheline in their CIPW norms. Alkali basalts are typically found on updomed and rifted continental crust, and on oceanic islands such as Hawaii, Madeira and Ascension Island.
Carbonatitic magma was probably separated during the differentiation and crystallization of syenites and alkali basic rocks. The primary silicate magma was enriched with alkalies, carbon-dioxide, calcium and deficient with silica. During the alkali syenite crystallization, the carbonate portion of silicate magma was separated forming carbonatitic magma. Alkalies were already linked with feldspars and feldspathoids both in alkali syenites and in metasomatic fenites to be contained by residual carbonate. That is why carbonatites contained very low alkalies. The carbonatitic magma, after the melt separation, was intruded in Karroo sandstones, or earlier formed fenites.
The waters of Alkali Falls are located in the heart of Alkali Meadows. The waterfall is upstream of Alkali Creek, a narrow width creek that drains into Muir Creek, which in turn is a tributary of the Rogue River just south of Alkali Creek. The Alkali Falls trailhead is USFS No 1055 that spins off Forest Road 6540-900 from Oregon Route 230.
Alkali Lake is an unincorporated community in the Cariboo region of the Central Interior of British Columbia, Canada, located 40 kilometres south of the city of Williams Lake en route to Dog Creek and the Gang Ranch, at about 780 m (2560 ft) above sea level. The settlement, and the adjoining reserves of the Alkali Lake Indian Band, get their name from Alkali Lake, which gets its name from an outcrop of alkali on the hillside above it; the lake itself is not an alkali lake.
Juvenile hormone (JH) analog methoprene can serve as a possible limiting factor for alkali bees since female bees are more likely to reach reproductive maturity with JH. Alkali bees are also considered solitary bees because females have their individual nests and live alongside other female alkali bees.