Gadolinium has the highest thermal neutron capture cross-section of any element. The neutron capture reaction yields beta particles and several gamma rays having total energy of about 8 MeV. Delayed coincidence and pulse shape discrimination techniques can be employed.

The main applications of BC-521 and BC-525 are neutron spectrometry and neutrino research. Both are formulated with high flash point solvents because they are often used in large volumes.

BC-521 is formulated to yield the highest light output possible as well as long-term chemical stability. The standard gadolinium concentration is 0.5% by weight, but other concentrations up to 1.5% can be supplied. Since the liquid is normally used in large tanks containing several hundred liters, it employs a high flash point solvent for safety purposes.

BC-525 scintillator, with its mineral oil component, has a higher light transmission and higher flash point than traditional gadolinium-loaded liquids. It is also more suitable for use in large tanks containing acrylic plastic components. BC-525 is available with gadolinium concentrations up to 0.5% by weight.

Scintillation Properties	BC-521	BC-525
Gadolinium Content	0.5%, w/w
Light Output, %Anthracene	68	55
Wavelength of Maximum Emission, nm	424	425
Decay Time, short component, ns	3.6	3.8
Bulk Light Attenuation, meters	>4	>4.5
Density g/cc	0.89	0.88
Refractive index	1.50	1.49
Flash Point	44°C	81°C
Atomic Composition
No. of H Atoms per cc (x10²²)	5.25	6
No. of C Atoms per cc (x10²²)	4.00	3.85
Ratio H:C Atoms	1.314	1.56
No. of Electrons per cc (x10²³)	2.97	2.99