The phrase "a relatively small quantity" is correct and usable in written English.
It can be used when discussing amounts or measurements that are considered minor in comparison to a larger context or total.
Example: "In the experiment, we found that a relatively small quantity of the substance was needed to achieve the desired reaction."
Alternatives: "a modest amount" or "a minor quantity".
Mere possession of a relatively small quantity of crack means a five-year sentence.
Only a relatively small quantity of sainfoin in the diet is required to prevent bloat.
A relatively small quantity of the coal is pressed into briquettes for domestic heating.
Another significant property of the proposed method is a relatively small quantity of fluid required.
Application of MC requires a relatively small quantity of suspension (about 2 ml).
Preliminary estimates of night time operations indicate it is possible to achieve over 10 h of operation with a relatively small quantity of Silicon.
While the most contaminated sites (such as Hanford) have received the most attention, there are examples of USA sites where contamination involving relatively small quantities of Pu (such as an estimated 86 g of Pu at the Rocky Flats '903 Pad') have nevertheless received costly remediation.
For example, he wanted to include Wi-Fi with the first version of Bug Labs' product, but he couldn't find a company willing to supply chips in the relatively small quantity he needed.
In the few hundred cord-blood transplants that do take place in this country each year, children are the most frequent recipients, because of the relatively small quantity of stem cells typically yielded by a single umbilical cord.
The major obstacle in studying histone modifications from primary cells is the relatively small quantity of cellular material available.
Another possible reason was that the PCR-DGGE approach, unlike establishing clone libraries, could not detect minor phylotypes of relatively small quantity despite of its own advantages.
