Socially acceptable to email a connection of a connection requesting information? I'm interested in knowing the optimal technology/techniques to implement something (storing Lidar data in a database) in a corporate IT world. I have a colleague who recommended that I contact his old phd adviser since his old adviser has done what I'm looking at doing before. He carried out the work as a means to an end for his research and the work I'm interested in is not his research itself. I believe they parted on less than perfect terms and my colleague has said mentioning him might not achieve anything productive as a result (I suspect this wouldn't be too bad as it is simply a referral from a colleague and was a while ago).

So, is it generally regarded as acceptable to email this old phd adviser of his with or without mentioning the referral and ask him if he would mind answering 3-4 basic fairly high level questions regarding the work he has previously carried out? Since acceptable depends on how it is written, what are some good techniques for writing cold email requests for information in this sort of scenario? 

NOTE: This is in academia primarily because I'm wanting to email a professor and ask about information he has worked on that he carried out as a means to an end.
Ideally the person who knows both of you would write a short introductory email and send it to both of you.  You could request that he do that.

If he doesn't do that, you can still mention that he suggested that you write to this person at the beginning of your email.  Just use a succinct, mildly friendly, and professional tone, and you'll be fine.