I am Siegfried Muche, engaged in selling Copper sulfate in Russia, thus, it is extremely important for me to select a reliable supplier of Copper sulfate.
Shipping and Payment
In order to meets different needs of buyers, according to intercoms, Copper sulfate suppliers often provides several payment ways, such as FOB, L/C, D/P, T/T and so on.
Exquisite Website
Qualified Copper sulfate suppliers tend to have more elaborate and professional web site, with better user experiences and less bugs or faults.
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. 
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.
Warehouse
Warehouse is also important for Copper sulfate suppliers, Copper sulfate traders make judgments through Copper sulfate market situation. On one hand, while Copper sulfate is in the upside, traders purchase bulk Copper sulfate for storage, and sell with the price advantage; On the other, vendors need to keep cargo in warehouse in case customers need LCL loaded.
Foodchem International Corporation owns an EDC warehouse in Shanghai, an advanced warehouse system which only few trading companies in Shanghai can provide, it avails fast delivery within 1 week.
Certificate
A formal operation supplier of food additives normally passes ISO certificate as well as other well-known certificate like halal, kosher, ect.
Location
Generally cargo takes ship delivery; thus, sustainable trading companies tend to set their sites in coast cities, such as Shanghai, Qingdao, and Tianjin in China.
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.