Tin (II) Chloride, SnCl₂

Despite its being a simple inorganic compound, Tin (II) Chloride is notoriously difficult to make in high purity, and this is reflected in its usually high price on the market, even for indifferent purity grades. The difficulties stem mainly from three facts: firstly, that SnCl₂ is a fairly potent reducing agent and is therefore sensitive to atmospheric oxygen and other contaminants, especially at elevated temperatures; secondly, that Sn(II) compounds can disproportionate readily into Sn(0) and Sn(IV); and thirdly, that it is also prone to hydrolysis, decomposing to the basic chloride Sn(OH)Cl plus HCl. As a result, most of the less expensive commercial grades of SnCl₂ from the majority of manufacturers contain significant amounts of basic chloride and/or Sn(IV) compounds (usually beta-stannic acid), in addition to various metallic impurities which often render them unsuitable for plating and other high-purity applications, such as catalysis of organic reactions, organotin chemistry, the textile dyeing industry (where impurities would corrupt the colour of the dyes), and opto-electronic coatings.

The 'industry standard' method for producing high-purity Tin (II) Chloride is to first manufacture a low-purity or 'crude' version of the product and then sequentially extract the major impurities in several steps. This process is time-consuming, costly, and fails to remove every impurity. The reason for the very competitive price of Dawnmist's Tin (II) Chloride is that we eliminate the separate purification process and directly synthesise the pure compound instead in a straightforward two-step process using dedicated and highly automated plant, developed by Dawnmist’s own highly experienced engineering team — a manufacturing process unique to Dawnmist Fine Chemicals.

Our unique manufacturing process for SnCl₂ combines synthesis in a protective atmosphere with in-vacuo dewatering (directly to the hemihydrate form) under special conditions which inhibit disproportionation and hydrolysis of the product, as well as permitting dewatering to be performed at very modest temperature to prevent unintended reactions. Additionally, the synthesis step incorporates a special treatment to strip out Arsenic (As), Antimony (Sb) and Copper (Cu), which are the major cationic (metallic) impurities found in refined tin metal. By combining this process with high-purity virgin tin as the starting material, we achieve excellent purity without the cost penalty usually associated with highly-purified SnCl₂.

Dawnmist's expertise with tin compounds grew out of our electronics work, developing our in-house Printed Circuit Board (PCB) fabrication process, and we have been using this process, including SnCl₂ manufactured by Dawnmist, for many years already -- so we have proven capability in this field and our product has proven performance in high-quality plating applications.

Quite apart from a formal assay, there is a simple way to demonstrate the high purity of the Dawnmist product compared with normal merchant-market Tin (II) Chloride -- just dissolve a sample of each in a very small amount of distilled water (circa 1 ml per gram). This forms a solution which is too concentrated to undergo spontaneous hydrolysis, but the common impurities, basic tin chloride (Sn(OH)Cl) and beta-stannic acid (SnO₂. xH₂O) will not dissolve. Typical commodity SnCl₂ shows a cloudy solution because of these impurities, while the Dawnmist product gives a perfectly clear solution. A similar demonstration can be performed by dissolving the compound in methanol, ethanol or isopropanol -- although hydrolysis is impossible in non-aqueous solutions, the same two impurities likewise fail to dissolve and will give a cloudy solution if present. You will also often observe a yellow tinge in low-grade product due to the presence of beta-stannic acid, whereas the Dawnmist product is pure white.

Because of the manufacturing process we use, the Hemihydrate (SnCl₂ . ½H₂O) works out as the most economical way to buy stannous chloride since it contains much less water (and hence more SnCl₂) than the Dihydrate, as well as being less expensive per kilo. Any process that calls for a solution of stannous chloride (dihydrate) in water (with or without other ingredients) can equally well use the more economical Hemihydrate: simply use 88% of the weight of dihydrate specified and make up the extra 12% with water. In other words, each gram of dihydrate can be replaced with 0.88 grams of hemihydrate and 0.12 grams of water. Once made up into solution, the result is identical but you save over 25% on the cost. And since our high-purity stannous chloride is already much cheaper than all our known competitors, you can make huge savings by switching to Dawnmist Fine Chemicals.

Hemihydrate has a second significant advantage over Dihydrate, and that is its convenience of handling and storage when in the solid form, prior to being dissolved. Dihydrate has an extremely low melting point, virtually identical to human body temperature, with the result that it readily becomes sticky and awkward to handle, or even melts completely, on a hot summer's day or in a hot environment. Furthermore, because it rapidly becomes (semi-)melted with body heat, dihydrate is much more unpleasant in the event of accidental skin contact. In contrast, hemihydrate has a far higher melting point and cannot melt accidentally.

For certain applications it can be helpful, for ease of handling, to have the compound supplied in the form of tablets of known mass instead of the usual granular form. We can supply the Dihydrate in this form to special order -- please contact us with your requirements for a quotation. Please note that for technical reasons only the Dihydrate form can be tabletted; the other forms contain too little water to be shaped into tablets with good integrity.

Safety Data (MSDS) and Other Information

MSDS for DFC-4011 (hemihydrate)		Link: Detailed data on SnCl2, from Wikipedia
MSDS for DFC-4012 (dihydrate)		Email our Technical Help/Information Service

The table below lists the pricing for small-to-medium quantities of product. If you would like a quotation for a larger amount, please contact us. Detailed ordering and payment information, plus contact points, will be found on the Fine Chemicals Main Page. Prices shown do not include shipping, which will be charged at cost -- please contact us for shipping costs to your destination. As an alternative to shipping, goods may be collected from our base in Exeter (UK) by the customer or their agent by prior appointment only.

All prices are listed in GB Pounds (£) per kg  -- we will supply any amount you choose, in multiples of 250 grams. Please contact us for quotations in other currencies or for quantities significantly larger than 10 kg.