Recently, I am learning the production of soluble and insoluble salts. My friend and I have done this experiment at the school lab.
We wanted to taste them to see whether they are salty are not. The teacher luckily stopped us from doing that.
So without tasting them, I would really like to know whether all salts are salty.
No. There are sweet, bitter, and various other salts. (Likely, there are tasteless salts too). Pure salty taste is as far as I know exclusive for table salt, though I wouldn't bet on it.
Lead and Beryllium salts are said to be sweet, though toxic. Epsom salt, $\ce{MgSO4}$, is bitter. $\ce{CuSO4}$ has an incomprehensible, persistent metallic taste. (Based on personal experience. Copper salts are slightly toxic, but not extremely, so I survived with no consequences.)
Salts with hydrolysing cation (various alums) are acidic in addition to other notes.
Saltiness is perceived when alkali metal enter taste buds.
From wikipedia:
Saltiness is a taste produced primarily by the presence of sodium ions. Other ions of the alkali metals group also taste salty, but the further from sodium the less salty the sensation is. The size of lithium and potassium ions most closely resemble those of sodium and thus the saltiness is most similar. In contrast rubidium and cesium ions are far larger so their salty taste differs accordingly.[citation needed] The saltiness of substances is rated relative to sodium chloride (NaCl), which has an index of 1. Potassium, as potassium chloride - KCl, is the principal ingredient in salt substitutes, and has a saltiness index of 0.6. Other monovalent cations, e.g. ammonium, NH4+, and divalent cations of the alkali earth metal group of the periodic table, e.g. calcium, Ca2+, ions generally elicit a bitter rather than a salty taste even though they, too, can pass directly through ion channels in the tongue, generating an action potential.
[citation needed], or include the links, or at the very least hit enter once to preserve the paragraph breaks and make it a little easier to read. That will make it easier for you to argue that it "takes time to research an article".
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permeakra is quite right with his counterexamples of salts that don't taste purely salty, but I'd like to expand on why. We haven't fully identified and elucidated the receptors involved in taste, but they can be broadly classed into tastes people are familiar with: salty, sweet, sour, bitter, and umami.
Salty and sour receptors are both known to be mostly dominated by ion channels, where salty receptors allow small cations to pass and sour receptors are sensitive to pH in a similar fashion. The other receptors are g-protein coupled receptors. The trick with taste (and smell, for that matter) is that there is not a single receptor type for each possible chemical one can taste, i.e. there's not a receptor entirely selective towards $\ce{Na+}$. The way it works is that there are many types of taste receptors that are somewhat selective to specific classes of molecules and a given molecule may induce a response in many different receptors. The brain takes all the data from all these receptors; combines them; integrates information from the nose, eyes, ears, tactile nerves in the mouth, etc.; and then produces the sensation of taste.
Thus, though both $\ce{Na+}$ and $\ce{K+}$ will stimulate some of the same saltiness receptors, they also stimulate other receptors and in different amounts, making them taste different. In general, small cations can stimulate the ion channel receptors for saltiness, so many salts do taste salty to a certain extent, but many also stimulate other receptors. Because what we perceive as taste comes from the interaction of all these different receptors (as well as other senses), one salt may taste very salty and another quite bitter, despite both activating saltiness receptors; the responses are not independent (which is why it's possible to mask overly salty soup or whatever by adding sugar).
The short answer is no, as suggested in the various comments. Not being a biologist I cannot give any underlying theory to explain this, but from personal and reported tasting I can give some examples: Copper sulphate, iron(II) sulphate, aluminium sulphate among others are very bitter. One you could try yourself would be sodium carbonate (washing soda) or sodium bicarbonate (baking soda). Interestingly Lead acetate as mentioned in one of the comments has a sweet taste which makes it particularly dangerous due to its toxicity. Even potassium chloride (used as a substitute for salt to reduce sodium intake) tastes quite different.
As mentioned, while not all salts taste salty, many do, and not just salts with sodium ions. If you want to try another edible salt, try to get ahold of ammonium chloride, which is used (both as a powder and otherwise) in sweets in the Nordic countries, the Netherlands and Germany. Its taste can definitely be described as salty, but not the same kind of salty as sodium chloride.
Ionic forms of some organic compounds that you will perfectly know, which can also be considered salts, have sweet taste, like sodium saccharin or sodium cyclamate, which are used as "artificial" sweeteners. The latter is considered to be about 50 times sweeter than sugar itself.
I wrote an answer to this question eight years ago concerning the taste of ammonium chloride, but as I've tasted quite a few different salts since then I'd like to mention some prominent examples, demonstrating that salts can have quite a wide variety of taste profiles. All the salts were purchased in bulk from reliable suppliers to the culinary industry, and I've tried all both as powders and dissolved in water. In the following, "salty taste" is short for "tastes like sodium chloride".
Ammonium chloride (NH4Cl), which I discussed in my other comment, tastes quite salty indeed. Of the salts I've tasted, it's the only one that tastes roughly as intense as sodium chloride at roughly the same mass – most edible salts seem to taste less intense. Erik Kowal suggested that its taste is a combination of saltiness (like sodium chloride) and an element of umami, and it's possible that there's an element of umami there (although its taste doesn't have much in common with pure MSG). Personally, I'd rather describe its taste as a mixture of salty and sour and an indescribable airway-clearing pungency that's hard to describe. It's certainly very salty, though: if you tasted the typical Scandinavian mix consisting of ammonium chloride, sugar and liquorice powder you'd swear there was sodium chloride in there, but there (typically) isn't.
Potassium chloride (KCl) is used as a replacement for (sodium chloride) table salt, and is the most common potassium salt used as a dietary supplement for people with low potassium levels and to prevent potassium deficiency in people taking certain kinds of medications that reduce potassium levels. My main impression of potassium chloride is that it has a much less intense taste than sodium chloride (both as a powder and dissolved in water). It has a mild salty taste, and even milder bitter undertones. When equal parts (by mass) of NaCl and KCl are dissolved in water, the taste of the NaCl almost conceals the presence of KCl, but the combination is less salty tasting overall.
Magnesium sulphate (MgSO4; also known as Epsom salt, used most prominently as bath salts but also sometimes in food and brewing and occasionally as a dietary magnesium supplement) combines a medium intensity salty taste with an intense bitter flavour. The bitter taste lingers in the mouth for several seconds. Not very pleasant, although not nauseatingly vile (depending on your tolerance to vile flavours) and tolerable at low concentrations.
Magnesium citrate (C6H6MgO7; medically used as a laxative; commonly used as a dietary supplement) only has a mild, "round", slightly soapy taste at first, but develops an aftertaste that I'd describe as that of stale or even rotten milk. Quite vile indeed, and the aftertaste lingers for a long time and is hard to conceal. No salty notes to its taste at all. Trimagnesium dicitrate is also relatively common, but I haven't tried it.
Trisodium citrate (Na3C6H5O7; usually just sodium citrate) is commonly used in food as a flavorant or preservative. A decade ago, trisodium citrate was popularized by a recipe (that came out of the "molecular gastronomy" movement) for a cheese sauce consisting only of water, cheese and trisodium citrate, where the trisodium citrate acts as a stabilizer to prevent the fats in the cheese from separating. Trisodium citrate has an inoffensive taste (at equal mass) consisting of a mild salty flavour, a slightly sour flavour and maybe a tiny bit of soapiness. The taste is easily concealed, and when trisodium citrate is present in food it's hard to notice even if added in greater amounts than table salt usually is.
Sodium bicarbonate (NaHCO3; baking soda; also commonly used as an antacid) has a taste that I would describe as sour, soapy and slightly bitter – not a very strong tasting salt but absolutely noticeable in sufficient amounts, as anyone who has added too much baking soda while cooking or baking can attest to. I described it as "sour", which I stand by, but sodium bicarbonate is obviously quite basic and not acidic! This is an example of the fact that there is no strict relationship between general chemical properties like acidity and how something tastes (in this case, "sour"). Certain online comments would have it that acidic compounds always taste sour and basic compounds always taste bitter, but many of the most bitter compounds are insignificantly basic and sodium bicarbonate certainly doesn't just taste bitter.
