I am Roshan Indika, engaged in selling Copper sulfate in Russia, thus, it is extremely important for me to select a reliable supplier of Copper sulfate.
Google “Company Name”
A renowned company name usually shows a great deal results on Goolge Search, because its company name is frequently searched by their customers or cited by other web sites.
Take “Foodchem International Corporation” as an example, as has been showed in the below picture, there comes out more than 298,000 searching results on Google. 
Size of Team
Member Size of suppliers or manufacturers also plays a very important role; generally number of manufacturers is slightly larger than traders. A complete overseas trade involves a lot of sessions; To perform perfectly, each session requires well-professional persons. A well-founded overseas trading company generally includes online marketing, sales, logistics, purchasing, service, administration departments, etc.
Normally we can scan through the vendor’s web site or some third-party social networking sites to confirm suppliers’ team size.
History of Supplier
History counts for a lot, a supplier with long history in the Copper sulfate industry has a wealth of experience to accurately grasp the Copper sulfate market, most of unexpected problems can be solved timely and accurately. The Chinese government gives all the enterprise a issued business license, from which history of enterprises can be found. Under such a fierce competition of Copper sulfate market, enterprises who can survive over five years can normally be trusted.
The picture below shows the license certificate of Foodchem International Corporation, China’s leading supplier of food additive and food ingredients with establishing year of more than 8.
Supply of Products
Compared with Manufacturers, other than service advantage, main advantage of trading companies lies in being able to provide various kinds of products. For example, when we would like to order Copper sulfate as well as several other food ingredients, trading companies becomes the best choice, since unlike factories, traders can provide one-stop service and have greater bargaining powder which permits a lower price.
Of course , we can purchase Copper sulfate directly from manufacturers if the volume is large enough, but it won’t be a bad choice if we keep in touch with some large-scaled traders. Because once your long-term-cooperate factory is in short of Copper sulfate , we can turn to trading companies, who can help to find other suppliers shortly or even direct supply Copper sulfate in no time.
As far as we know, big suppliers of food additives and ingredients can basically provide more than 100 kinds of products, among which, Foodchem International Corporation are able to supply overseas customers more than 300 kinds of food additives and ingredients, plant extracts, nutritional supplements, apis, etc.
Company Name
As a professional trader or manufacturer of food additives, normally its company name has food, chemical, additives or other key words in it. Other trading companies who have affairs in all fields, usually performs unprofessionally.
Google “Website”
While Googling a company website, there will be attached links along with the website on result page. It is an effective and reliable route to judge company scale and brand awareness since not a single company is able to impact Google’s objective valuation towards any company.
Exhibition
Copper sulfate suppliers will never ever lose the opportunity to communicate with customers face to face on exhibitions. Although with rapid development of the network, some people choose not to attend exhibitions, while substantial companies still avail these opportunities to meet their clients and looking for potential clients.
Therefore, exhibitions provide a efficient solution to find Copper sulfate good suppliers: Visit suppliers’ websites to see their participation in the exhibitions.
Certificate
A formal operation supplier of food additives normally passes ISO certificate as well as other well-known certificate like halal, kosher, ect.
http://www.foodadditives.com/Inorganic%20Salts/Copper-sulfate.html